I'm joining a clan and i wanna put one of my replays in my reply how do i do that?

This doesn't belong in support, but i'll answer it anyways.
Under your post, there's a button named "Go Advanced". Click on it, and under your post, there should be a tab named "Additional Options". Under that, there's a button named "Manage Attachments". Press on that, and spot the replay you want to upload.

[My Computer/Local Disk/Games/Toribash folder/Replay/Select your replay(s)/Press upload.]

The Tb uploader was recently down. It may still be. If so, simply upload your replay to a site like rapidshare, rghost or megaupload. it all works the same.