What product(s) are you attempting to install? If you just want the SAS Client software, you shouldn't see prompts for sastrust or sasadm - verify your selection of machine if you're using a plan file.
If you're after a larger offering, you will find more details in SAS(R) 9.4 Intelligence Platform: Installation and Configuration Guide
http://support.sas.com/documentation/cdl/en/biig/69172/HTML/default/n05020intelplatform00install.htm
It gives some information about the prompts you're seeing, with links to more details about setting up users.