Create a new page and call it Template: What Ever You Want Your Userbox To Be Called. If not already, switch it into source mode then copy and paste this code on to the page -
Replace the NAMEOFCOLOR with any color you want. For the border though, you must keep the SOLID before it and then place the color. For example, solid blue, solid red, solid grey.
Where it says NAMEOFFILE, place the name of the file. (For example, believemebrother.png)
Where is says SAY WHAT YOU WANT TO SAY, you put your own personalized text.
Where you see numbers followed by px you can change the numbers to your own personalized setting. (For example, I can change the border width from 3px to 8px. I can change the size of the file from 70px to 140px)
Click publish once you are finished.
To post a userbox on your page from the Userboxes page, put the code between four brackets.