You can use OBS Studio to create recordings of your entire screen or specific windows. To get started you'll need to do a little bit of setup. The first thing to do is set your recording options. Then you'll set up your canvas with what you want to record.
When you open OBS Studio for the first time, you will see an auto-configuration wizard. You'll set some initial recording settings. You'll only need to do this once. If you ever need to re-run the auto-configuration wizard, you can select it from the Tools menu.
To start recording video you need to specify a capture source.
Once you've set your recording options and capture source(s), you can hit Start Recording to begin. When you're done, click Stop Recording. A video will be saved in the Videos folder in your Documents folder. Whenever you exit and reopen OBS, it will use the settings you used last time.