4 answers
option 1:
on your salesforce screen, click on the cog wheel icon on the top right, pick 'edit page' , than on the page builder click on the related lists componenet.
now you should see a list of page layouts on the right hand side. Click 'view all layouts' and that will open the page layout editor, pick the right layout and now on the editor go to the 'relted list' area
option 2:
open the setup menu, switch to object manager, select the opportunity object, pick 'page layout' continue as above
