First of all you have to download the app Screen Recorder. You can download it by this link - https://play.google.com/store/apps/details?id=com.kimcy929.screenrecorder
Now open the app.
You can change the settings by tapping settings icon.
There are many more options in settings like time delay before recording, recording engine, magic button, stop options, pause recording when screen off, file name format, save file prefix, resolution, orientation, bitrate, frame rate, video encoder, record audio, audio bitrate, audio sample rate, audio channel, audio source, audio encoder, fix audio video async, show touches, auto create new file, floating toolbox, banner text, logo image, show camera, format and quality, night mode schedule, dark notification, The dot icon, and last language you can select.
If you want to record screen of your smartphone then tap on record button
You can pause or stop it by sliding down the Upper slide bar. You can comment below if you have any queries..