How to keep a copy of live video
In your OBS Studio software, press Start Recording, after pressing Start Streaming.
That way you will not miss anything. You can cut content that you don't think is relevant in post-production.
How to change where my video file is saved
In Settings, select the Output tab.
Under the Recording section, you can modify the Recording path by clicking on Browse.
Modify the recording parameters according to what you want.
Click Ok.
WARNING!
To both stream and record a live video, you need a high-performance computer!