Unless you have a DVD, you will have to get on a computer that has Internet access. Log into the Customer Portal and go to the Downloads section. Download the Installation Manager and walk through it. One of the options you'll want to look for is Individual installation and Download only so that you can get the installation files. Then transfer those to your non-connected computer and install away.
If files are missing, make sure you've got a good connection or let it run over-night when there's less activity. The download can be 3-5gb in size.