I'm going to assume you're talking about Perfect Player on Android, look at this video screenshot: https://i.ytimg.com/vi/vA39wui6pAM/maxresdefault.jpg you see the little square next to UK | Movies? Press that, you will then get a menu in middle on the screen, you should see "Search Channel". I think on the fourth option. I mostly use Perfect Player on a touchscreen device, so not sure how you would do this with a remote but you will see a list of the channels pop up with Symbols, Numbers, then Letters on the left. To search for a channel like NBCSN you would, on a touchscreen, scroll down the list to N and press it, then it will filter all channels beginning with N, then you will find B and press that, again it will filter down the channels now beginning with NB, obviously next is C and you get the idea. If there were no other channels beginning with NB then that would have been the only channel showing up. Not sure if there is a way to get a keyboard to pop up, that would make typing in the channel easier, maybe you are using a device with a remote to type it in? But anyways it's pretty easy after you figure it out once.

If you don't want to use the smarters type of apk's instead of perfect player I would suggest progtv. Since using progtv I can't go back to perfect player.

Firestick?

Try the Vader's APK.

Alternatively, there is a search option if you can get past the clumsy touch controls. On the top part of the screen there is an icon for the menu.

Click that and the menu will pop up with a search option.

I don't know why that app is recommended here so often. The UI is awful. Never tried it with an android box and a remote, but for phones and touch it sucks.