To create a new user, connect to the server (how to connect to the server) and right-click on the Start button. Select Computer Management

In the window that opens, click on Local Users and Groups - Users - right-click in the area with a list of users and select New User... in the context menu

You can also uncheck the User must change password at next logon checkbox.

The user has been created.
Now let's give the new user access rights to the server via RDP (via "Remote Desktop")
To do this, open the properties of the created user, go to the Member of tab - click Add and in the window that opens, the Advanced button

In the window that opens - Find Now - select with the mouse Remote Management Users - the OK button.

OK again

and once again Ok.
The newly created Windows Server user can now connect to the server via RDP.