To create a new relationship with a partner yourself, select ‘Add new relationship’ from the Relationships menu. Choose for which of your entities you want to create the relationship. Partners that are on CoorpID (subscribed partner) can be selected from the drop-down list.
Even with partners that are not making use of CoorpID (basic partner), documents can be shared. Select ‘Share with partner not on the list’ and fill in the name of the partner.