ill do it a little bit more prescise.
click on the
button.
scroll down until u get to a button which is named "manage attachments"
click on it, new window should pop up. now click on one of the "browse" buttons. another window should pop up, search there your toribash > replays folder. (usually is toribash at C>Games>ToribasX.XX, where X.XX stands for the version youre using)
after u got all your replays there, simply click "upload". wait till its finished and then simply post a normal post with your stuff.