Once you click the plus button you will be approached with a screen that will ask you what you want to record with OBS you are going to need to click on display Capture and it will ask you what you want to name it. Go ahead and name it Monitor. Once you name it, it will bring up a screen that says what you want to record. Now you can’t change it yet but you can change if you want to capture the cursor or not. Now that is up to you on what you want to capture the cursor or not. Now once you have a capture you will see a button that says record, whenever you want to record something just click that button and it will start recording, now if you want to have a hotkey you can just click >Settings >Hotkeys >Start/Stop Recording and press any button on your keyboard that you want to start recording with.