where to install?

Is this Aeigr module installed into /var/aegir/hostmaster-7.x-3.0/modules or /var/aegir/hostmaster-7.x-3.0/sites/all/modules or is it installed to each site in the /var/aegir/platforms/platform/sites/all/modules folder. Or somewhere else entirely?

I'm new to Aegir and I can't seem to find any documentation on installing modules for Aegir itself. Thanks for your help.