Hi Marike,
as far as I know the actual licence policy of SAG the ARIS Basic version has only one project room (this is what you choose during login), and there are no options to create another one. This is one of the limitations of ARIS Basic (nearly no customizations possible e.g.). If you need more you have to go to ARIS Advanced.
To be honest I am not happy with these restrictions.
Regards
Klemens