Please chack the way. If it doesn't work you can't edit that media item. Let me know then and I can edit what you need.
1. Click the Media on the top bar of the main forum page.
2. Select the "Your Content" or "Your albums" option.
Depending on the option you chose above ...
3. If the "Your content" was chosen , browse images and find the the pic you want to edit. Then click it and go to the step 4.
3a. If you chose the "Your albums" , browse and find the album with the image you want to edit. Click the album.
3b. And then choose ( just click ) the pic for edition.
4. On the next opened page find and select the option "Edit".
5 If there is not the option displayed, click the three dots and small triangle on right for more options.
5a. Choose the "Edit Media Item" option.
6. In the pop up window edit the info you need to. The top line is the pic title while the bottom one is the description for the image. If the description has already been added it should be in the bottom line too.
7. When all is edited, please hit the "Save" button.