How to implement our custom design in suitecrm?

Hello all
I want to implement my custom design in suitecrm.
what is the procedure to do that .
I copied SuiteP folder from modules/themes/SuiteP
to /custom/modules/themes/SuiteP but inside css folder it shows all the themes like Dawn,Day,Dusk,Night etc .
where should i do my own design so that it becomes upgrade safe and looks good.
Now in which file i should write my own CSS ??

I am writing some CSS inside /modules/thems/SuiteP/Css/normalise.css and it works fine.
but when i copy SuiteP folder inside /custom/modules/themes/ and write css inside normalise .css then it won’t works why is it so ?


Have a look at this post

ok thanks . if i would like to edit (adding custom css) Day sub theme in my custom/themes/SuiteP/css/Day folder then this will be upgrade safe right ?

Yes, what you create in custom should be upgrade-safe.

By the way, don’t call your new subtheme Noon, call it something else, because there’s a subtheme with that name coming to SuiteCRM core very soon, it’s a high-contrast theme.

Ok by the way If i can edit already existing theme let say Dawn then no need to create new sub theme i think .
Thank you @pgr