I would like to update the version of the following package: https://packages.ubuntu.com/lunar/rbenv in the official repositories. Which steps would I have to take so that everyone would have a newer version of this package.
I would also like to add a screenshot to the package page.
rbenv is packaged at Debian, so one thing you can do is to send a message to the debian-ruby mailing list with a reminder that a newer upstream version is available. Maybe also ping some member in Ubuntu’s MOTURuby team. @lucaskanashiro (just did that 
).
See https://tracker.debian.org/pkg/rbenv
A great deal of volunteer work is needed. Time to get involved, join that mailing list and pick away at the actions needed. When a new upstream release can be successfully packaged, it will flow into a future Ubuntu release.
Thanks for both replies! Both are great and give me direction. Which one should I mark as a solution?
Neither is a true solution. Both are guideposts and resources.
You are just starting the road to a solution.
You could mark neither --or either-- as a solution. It’s really up to you whether you think it helped. Were it me, I would choose neither since…well, I said it in the first sentence already. But it’s not me.
Haha you’re right 
I know neither is a solution. I just wanted to know whether I should mark one as a solution for the others.