How does one earn coins for gifts?

If you have been asking and answering questions, you have coins. Participation is what esrns coins. Click on t three little lines in the top right corner next to your avatar. Accumulated coin count will be the first item in the drop down menu.

Click on the three lines next to your profile pic top right, it will tell you how many you have.
You earn them by posting.

I got some. I don’t know what to do with them. I don’t think I can transfer

Post, interact, login. Don't get into pissing matches. Or they kinda prefer you buy them, I'm sure

Post questions and respond to other posts

Ait adds slowly but surely

When you post and reply to posts you get coins

https://similarworlds.com/questions-submit