Thanks for helping,i appreciate your reply.
When you read a post, at the top of the post page, you'll see a Watch this Discussion with a green add icon. It is next to the Email This icon and text and next to the description of the forum. Click the Watch this Discussion link and that particular discussion will be added to your watchlist.
I'm not sure what you mean by friend's activities. If you're referring to your home page, you cannot remove your friend's activities. You can remove all your friends if you want (by deleting them), but if they are your friends, their activity is displayed on your logged in home page.