How do you send another friend request on facebook if you rejected it before?

1. If you mean that the person rejected your request, then go to their profile. You will see Friend Request Sent. Click on that and underneath it will write on the bottom of the drop down menu Cancel Request. Click on this, then try to send the request again.

2. If you mean that somebody sent you a request and you rejected, just go on the friend notification bar and click see all friend requests you will see it there.