Subscribe contacts to an email group via list upload

I'm quite sure this question has been asked before but I can't seem to find a thread. Apologies in advance.

I've also did a few rounds of Google search on the topic. The suggestions seemed to be to create a programme for this. I tried, but the program canvas didn't seem to let me do what I wanted to achieve.

Essentially here's what I want to do:

• Upload a list (.csv file)
• Instead of the default 'subscribe globally', I'd like to subscribe the contacts to only specific email group(s), changing the contact's email group preference from 'No status' to 'Subscribed'