Shares/users can't get past windows sign in unless set to public

Hi, having real issues here.
I made a test user called tester.
I went to the share, and clicked for use the password.
So user name is tester and password is test1

When I go to my network and click on the tester share folder up comes windows security asking for network sign on.
Says enter your password to connect to mycloud etc.
When I type in tester and test1 I get access denied.
I’ve tried my windows log on name and password but this is rejected also

What am I supposed to type in at this point please?

The instructions say your routers credentials?

Please help