This seems to be your first post on Microsoft Dynamics GP Community, allow me to welcome you on behalf of my colleagues
Regarding your issue accessing customer source, I would ask you to access the following link ; Microsoft Dynamics Customer Source . Once you are logged in, use your windows live account (which has already been linked to customer source by your partner). Enter your window live ID credentials.
The steps are quire easy, you may refer to the post below for a step by step guide on How to gain access to Microsoft Dynamics CustomerSource
Otherwise, you may refer to your partner for answers.
Welcome again to the community,
please never hesitate to share any further inquiries