Connect to Oracle database as apex_version user

I'm talking about schemas like APEX_040200, APEX_050100, APEX_180300, APEX_190100 etc. I'm trying to install an APEX Plug-in that is being installed from a script, where developper commented Assumes you are running the script connected to SQL*Plus as the Oracle user APEX_040200 or as the owner (parsing schema) of the application. I have APEX 19 installed, so it's APEX_190100 then. Empty password didn't do the trick, default password I don't know. Is there a way to change it's password harmlessly? Or are there any ways to install this plugin to the whole APEX instaince, not only to a certain workspace?