Can some one tell me if I can edit a previous post as I have just put another comment there.TIA

Hover your mouse next to your login name at the post. A little flag will appear and the word edit. Click on the edit and I change what ever your need in your wording.

Or click on the little arrow at "add comment" and a edit button will appear also. All depends if you are in a original post or one where you had added a comment. Hope this helps.