Payment methods and procedure
Expand "Step 4. Payment Method" at bottom of the check out page to show the Paypal / Credit card icon.
If you have an account with Datrex or want to call in your credit card select "On Account"
To use PayPal just sign in to Paypal and follow their instructions
To pay using your credit card click the grey "Check out as a guest" button and follow the instruction
Below is a sample of the page and what to select.