First, you must configure your TCP/IP connection to use your modem as the default gateway. The procedure for this varies slightly depending on the operating system you are using, but the settings you will need to use are as follows:
IP Address (of your machine): 10.0.0.1
Subnet Mask: 255.255.255.0
Default Gateway: 10.0.0.138
IMPORTANT: make note of the current settings before you change them because you will need to change them back in order to connect to the Internet again.
Once you have done that, you may need to reboot your computer for the changes to take effect. Then you can type 10.0.0.138 in your web browser to access the modem configuration pages.
Note that you will not be able to connect to the Internet using your modem while doing this, so it is a good idea to have any material you need either printed out or saved to your computer since you will not be able to consult resources on the internet for assistance.