How do I delete a colony or reset to start new?

I messed up so much. How do I delete a colony? I have too many and not advancing? Also, I tried the ~ leave_galaxy and nothing happened even tho it said done. Please help. Thanks

You need to wait 7 days from the day you logged into the galaxy, and then on the menu when you hover over to join the galaxy, you will see the exit button on the top right

Thanks. How can you disband or delete a single colony?

By removing the population via transports.