When planning your video one thing to think about is your Call To Action (CTA) that you are going to use at the end of the video.
Either to subscribe, like, comment or to link back to your website. Because once you upload the video, you can also add these annotations, cards, and end templates.
While recording towards the end of the video, you can put an option to subscribe button using your "YouTube video manager."
Or you could merely say "subscribe below" with a verbal action, but if you want to put a subscribe button. You need to take a button.
Go to Google and enter "subscriber button youtube." Then click on "images." (upper left). And on the search results, take any button you want, downloaded.
And then put it on to your screen in your screen recorder software.
(Once you're inside the youtube video manager, then you can add that in.)
If this seems to confess as I said earlier, you can just say at the end of the video "Please, like to subscribe if you'd like to see my next video when it comes out."
To your success : )