One reason why just copying an organization's website into Wikipedia would not be satisfactory is that, as an encyclopedia, Wikipedia is selective about subjects for articles. The criterion used is called Wikipedia:Notability, and is not a matter of opinion but has to be demonstrated by showing "significant coverage in reliable sources that are independent of the subject." Significant means more than just listing-type mentions; reliable excludes Myspace, Facebook, blogs, places where anyone can post anything; independent excludes the subject's own website, affiliated ones and anything based on press releases. The test is, have people not connected with the subject thought it significant enough to write substantial comment about?
That has the advantage of being a more objective test than "Do we think it's important?" and also of ensuring that there are independent sources for the article. It is quite a tough test, and many worthy organizations, especially new ones, cannot pass it. That is not at all to their discredit, but it means they are not suitable subjects for a global encyclopedia. The test applies to non-commercial organizations and good causes, too - we have an explanatory essay entitled Wikipedia is not here to tell the world about your noble cause.
You presumably work for the organization. That gives you, from Wikipedia's point of view, a Wikipedia:Conflict of interest. As a general rule, a suitable page will be best written by someone without Conflict of Interest; it's not impossible to do it properly with a COI, but it's more difficult: you are automatically thinking in terms of what you want to communicate to the public, but an uninvolved person will think in terms of what the public might wish to know. Keep in mind that the goal of an encyclopedia is to say things in a concise manner, which is not the style of press releases or web sites, which are usually more expansive.
Think hard about notability. See WP:ANS for what it means. If you cannot find independent sources to establish it, you will be wasting your time and effort. If you want to go ahead,
- Read WP:Plain and simple conflict of interest guide
- Read WP:Your first article
- Click on Help:Userspace draft and fill in the title. That will start a draft page in your "user space" where you can work on the article, with a link to good advice and a "Submit" button which will send the article, when it is ready, to WP:Articles for creation, where an experienced user will look at it, and either accept it or give you feedback.
- When writing, make a strong effort to think of yourself, not as writing for the organization, but as writing for Wikipedia about the organization, from outside. You are not addressing a potential customer, but a general encyclopedia reader. Bear in mind the WP:Verifiability policy: "any material challenged or likely to be challenged must be attributed to a reliable, published source", and when writing any glowing adjective, or indeed any claim, imagine a hostile critic saying "Who says? Can you prove that?" Don't talk about the organization's aims and hopes for the future, or its mission statement, but about what is has achieved. No opinions, only facts, neutrally stated and cited to reliable sources. Write in your own words, without copying from the website.
Realise that this will not be your article: as soon as you post it, it becomes Wikipedia's article. Nobody "owns" a Wikipedia article, not its first author and least of all its subject. Others can and will edit it, and you will not be able to insist on your preferred version. If you want an article about your organization which you can control, this is not the site for you.
By now you are thinking "This is much harder than I thought, all I wanted to do was post a copy of our web-site to tell the world about us!" I apologise that (because we are anxious not to put new contributors off by making them read a lot of advice) Wikipedia does not make clear at sign-up time that it is not a "notice-board" site like Myspace or Facebook, which are set up for people to do exactly that; but if Wikipedia is a more valuable resource than Myspace, it is only because we have standards and rules on notability, verifiability and conflict of interest.
I have gone into all this at length not because I wish to discourage you, but to help you understand what is involved, and to avoid the common situation where a new contributor expends a lot of time, energy and emotion on what was always a hopeless cause. If you decide to go ahead, you will find many people willing to advise and assist you. There is a WP:Tutorial and a WP:New contributors' help page, and you can also ask for help by putting {{helpme}} (two curly brackets each side) at the bottom of your talk page with your question below it.