First thing you need to do is give the horse a reason to come to you!
You can start by going into the pasture and giving him a treat. Then leave. Repeat this several times (not necessarily on the same day). Give your horse a reason to WANT to see you coming! As time progresses, shorten the distance you walk TO your horse and ask him to come to YOU part way. You can close this distance over time, as the horse will come running to the gate when he sees you.
The following pictures were taken on a muddy day, after the rains. The horses generally hang out at the top of a hill. The pasture gate is at the bottom. The other horse owners usually have to walk up the hill to "catch" their horses, but I give a call and they come running down to the gate.
At the top of the hill snoozing.
They hear the call.
And start weaving down the hill.
Rounding the corner.
Do these look like horses who don't want to be caught? :-)