It takes time. If you have no existing repertoire do the following
as white
1. e4
come up with reasonable replies to the major 4-5 replies such as 1.. e5 1...c5
as black
1. e4 you play 1. e5
1. d4 you play 1. d5
stick to classical chess, focus on your objective in the openings - development, the center, space, king safety.
can any1 told me what is the best way or fastest to learn openings