Putting pictures on to forums can be a nightmare. It does depend on how good the guys are that write the forum software. Anyway this one is not so easy, IMO, as others. Basically you need to put your image somewhere such as Photobucket or similar then put the URL link on here. Yeah whats that all about. Other forums that I am on just let you add a picture directly from your computer.
Anyway on to your problem. You haven't said what OS you are using but windows ten has an extremely annoying, again IMO, little thing called Quick Access> This lists all the folders that you have opened previously in file manager. I say it's a pain because it also lists folders that you have opened from things like USB sticks that may not be connected to your computer at that time. Anyway to turn that of, if that is what you want to do, open file manager and left click on "file" then left click on "change folder and search options" on the general tab go to "privacy" and take the tick out of "show recently used files in Quick access." Hope that helps.