How to add start G-Code

[Andy.wpg]

I have been using PrusaSlicer for a couple of months, and I simply can’t find the start g-code.
I need to add M420 S ; after the G28 in the start.

On Cura, it was easy to find and use. With Prusa, not so much. Anyone feel like explaining it to a dumb dumb?

[kitedemon]

[kitedemon]

Under the printer tab side bar custom G-Code. you can edit as you please.