Once you have the programs properly installed on your server, and have opened the "admin.php" program in your browser, you'll be presented with "Step 1" of the browser based installation system. You should be able to follow the on screen prompts and information to complete the setup process without incident.
Note that the last step of the setup process will suggest a cryptic administrative password for you. If you elect to use the generated one, write it down, as it's most assuredly something that you'll not remember. If you choose to change it at this point, that's fine, but we do not recommend that you use your systems normal ftp/ssh password or your mysql password .... make this one unique.