Great advice from
@Heather White and
@Boris Qs
My 2 cents:
I'd also add "pinned comments" to the list. Go to the video page (the actaul page that the viewers use) and add a comment saying something like here are some other videos you may be interested in:
Video 1 title : LINK
Video 2 title: LINK
Publish the comment and then click on the 3 dots to the right of the comment and select PIN comment. - This will make sure your comment is the top comment.
Also, during all your videos, make sure you "casually" actually mention at least one other video. Example script: "I discuss XXXXXXXX in a bit more detail in my ' XYZ video' so I recommend you watch that for more info." (And then after you upload, create a card that links to that video at the exact moment you mention it.)