To upload an image to the forums the first step is to make sure that you are in Go Advanced mode on the Brit-Gen thread where you want to place the photo. Click on the picture frame in the row of images above the reply box. (6 from the RH side). The box that appears requires a URL address.
You have to upload your photo to a free site which will provide a URL address. I use Postimage which is very simple.
On the home page of Postimage click on 'Choose images' then find and click on the file you want to upload where you have the photo stored on your computer eg Pictures. Then click on the particular folder that holds your picture and Open it. Choose your photo, click on it and click on Open. You are now taken back to the Postimage page where you are given a choice of 9 links. Click on the URL 'Hotlink for forum' Now right click on the URL address and then click on Copy. Go back to the reply box on the Brit-Gen thread and in the URL box right click on your mouse and from the menu click on paste. The URL for your photo is now ready to be posted on the forum along with any information you have typed in to accompany it.
There are other free sites from which to upload images with URL addresses if you want an alternative.