Sam,
You must do a few things in advance before installing Moodle.
1. create a MySQL or Postgre database that has both a user name and password. For example:
- db name: servername_moodle
- db user: servername_samf
- db password: letmein
2. create a data folder (moodledata) outside the public_html directory for Moodle to store course and student resources. Give this directory write permissions.
These things must be done before you attempt to install Moodle, otherwise you will get the types of error messages that you are reporting.