Best steps to upgrade from MAC mini to iMAC

I am going to be upgrading to 27" 5k iMac in less than a week. I currently have late 2014 Mac Mini.

I have time machine on external HDD. I will have the ability to have both up and running at once.

Is there a document with steps to help with this move?

I will have all appropriate cables TB3 to TB2 or ethernet.

I have never done this before and want to get it right the first time.

Result is to set up mew iMac and continue working as normal.

Not sure if I need time machine connected to new iMac when it boots or not.

Any help is appreciated.