Still can't upload pics, gotta try and get someone to fix that.
It's not that complicated. On the website, click Settings under your username, then Edit Signature. From there, at the bottom, there are two options to Upload Signature Picture, web or computer. Pick one. After you do, the page will most likely refresh, and, right above the Upload Signature Picture section, but below the actual signature text box, will be a section that says Signature Picture and it will have a preview of it. To the right of the preview is a button that says Insert Signature Picture. Click that and it will add it to the signature text box above with the appropriate tag wrapped around it.