Problem with package manager

[malleechick]

Hi, I'm new and still finding my way. Your helpwould be appreciated.

I am trying to install Ad Manager via the package manager. On my admin panel, when I click Download Packages and then Browse (on Simple Machines Third-party Mod Site) I get:

Unable to connect to the server. Please try using this URL instead.

That url takes me to the mod site. So, two questions:
1. How do I download manually?
2. Why am I getting the error message?