You need a place on the web to host your pictures.
A place you can upload them too and be able to view them while on the web.
Some hosting places, unless you pay, wont allow "outside" links for things such as posting a picture in a forum post like you want to do.
You can't just link to them from your hard drive to the message your posting.
(based on the code I see on your posting, you are trying to link to the photo as it sits on your harddrive... that's a no can do. )
As mentioned above, to upload a photo you have to go down below the posting window (in advanced mode/not "quick reply" mode)
In quick reply mode, you'd need to have the photo on the web already and know the url for it.
On another forum I'm on,
www.photobucket.com is extremely popular.
The folks that don't now much about computers and the web use it to upload and store their pictures to share them and to then link to the pictures for use in posts on the forum.
Your ISP probably has given you space as well. . you can store photos there too. Just have to read their directions to access and upload to the space they gave you.
As mentioned above, resizing is important. Especially with the cameras common today, that take from 3 - 8megbyte size pictures if not set to a different mode.
For online you commonly want 640x480, but no bigger than 800x600 and not much more than 100kb in file size.
So you will need to learn how to resize and save your pictures to a reasonable file size (selecting the correct amount of compression) so it's a nice file size, but not too much compression so that it looks like crud.
I think Photobucket has all these tools on line as well. . why lots of folks on the other forum use it.