You are looking for the method to import the Custom Logo or texts into your productive system.
S/4 HANA Cloud
Reproducing the Issue
In S/4 HANA Cloud productive system,when open APP "Manage Logos",you
see the error "Changes not possible in productive system".
Edit custom texts and Logos are only permitted in development system.
Follow Chapter 5 in below setup instruction to transport custom objects from Quality to Productive system.
Manage Logos;Manage Texts , KBA , BC-SRV-FP-OM , Output Management: Form Services , How To