Hello France,
Its all good not being tech savvy, its simple to edit your signature and Ill show you how.
Step 1. At the search bar on the top of the screen click on forum actions
Step 2. Click on edit profile
Step 4. go down the page until you see edit signature on the left
Step 5. Click on edit signature
Step 6. put and text or image code that you want in the blank box
Step 7. Click save signature to save it and it will show up when you post