If you'd like to add a subscribe prompt to your links it is quite easy.
Copy your YouTube profile link.
Append to the end of it
?sub_confirmation=1
Then save the link.
So if you do not have a custom channel name it might look like this:
https://www.youtube.com/channel/UCGBl1CZRE4v5lU3WVvzuOzQ?sub_confirmation=1
Visitors will be prompted to subscribe when they open your YouTube Channel.
Video walkthrough: