There are two ways to include pictures:
1. the Manage Attachments feature allows you to upload the photo(s) directly, but the size of the attachment is limited to 100 Kb. I don't know how that works, really; compression must be involved, because sometimes I can upload a JPG that's somewhat larger than 100 Kb, and it still "comes in" under 100.

2. Put the photo somewhere else in cyberspace that has a URL that can be referenced (most people seem to use PhotoBucket, Flickr, or one of the other no-charge/low-charge image dumps online). Then use the little icon with the mountains and sun, yellow background. It will ask for the URL, which you just paste in. Then the whole photo will appear in the post inline, without a thumbnail. This is what most people do to include photos in posts, since the image is larger, and can be (it seems) any resolution you like. Only thing to watch out for is that if the photo is more than, say, 800 pixels wide, people with smaller screens won't fit the width. And another bad effect is that that the width of any image on a Bikeforums "page" of posts constols the width at which all posts on that whole "page" will wrap. This is annoying when some vanity photo takes over and makes it difficult to read all the other posts!

Have fun here, and welcome!