I find that it's easiest to do in source editing. Go to a gallery (some linked below) and find a userbox you like. Paste the template onto your userpage. If you use Template:Userboxtop and Template:Userboxbottom, it will create a nice home for your userboxes in the upper right corner of your user page. Just paste all the box codes in between. Here's an example of what the code of my userboxes look like:
"Edelweiss with a Star" award for new users who made one good edit (excluding vandals)
Editors who received the "Edelweiss with a Star" were 20% more likely than non-recipients to still be editing one month later; 13% more likely to still be editing one year later
Giving these brand new editors a symbolic award hypothesized to increase their "reputational capital" (recipients felt like their standing in the community was heightened)