Xbox ultimate game pass renewal

Hello all

There is lots of "noise" and I just kinda wanna get to the best advice so I am sure this has been done many times.

It's my first renewal having done the 3 year upgrade previously.

It's changed from what I understand to "core" etc.

I would like to renew again and stack the membership, keeping my current profile.

But how do I do this? I am sure it's similar to before but I understand the conversion rates are different.

Do I let my old one run out and rejoin or do it before it runs out?

Step by step please . Really appreciated