Okay, found the M20 Administration Guide but the PDF was locked for copying. So I have written out the procedure for you below.
With regards to the internal web page of the M20, there is a section called Fiery WebSetup. This lets you configure the M20 remotely, however this is only supported over IP and Windows. So since the IP is not yet set then we cannot configure remotely and will have to use the control panel of the M20.
1. Press the Menu button and go to the Functions menu
2. Scroll with the down arrow and press the button next to Reboot Server
3. At the setup message, press any key
4. Choose Run Setup
5. Press the button next to Network Setup
6. Select Protocol Setup
7. Select TCP/IP Setup
8. Set 'Enable TCP/IP for Ethernet' to Yes
9. Enter a valid IP address for your network
10. Enter the correct subnet mask for your network
11. If there is a router on the network you can enter this IP address in Gateway Setup
12. You can now save and exit the Network Setup but while still in Network Setup you can enter Service Setup
13. Enter LPD Setup and set 'Enable LPD' to Yes
14. Exit from Service Setup and then exit from Network Setup
15. Then select Exit Setup. This will reboot the M20