First off using a 2 wire phone line for a 10mb network connection may give you less than desired performance. With that said,
It looks like this is using your existing phone line as a 10mb network cable. So my guess would be you plug that into a usb port on a computer that has been configured to access the internet thru your DLS connection. You will probably have to install some sort of network sharing software (hopefully provided).
You need to keep the DSL line plugged into whatever device its presently working on (modem, router, etc). Im guessing you would need another of these devices on the other computer that you want to share the DLS connection with, which would require its own connection to a phone jack as well. So....
Quick run down of the setup. Define PC1 as the pc that is connected to the active, working dsl line. Define PC2 as the computer you want to share the DSL connection.
First make sure you have internet access on PC1, web surfing, email etc. Then plug this usb device into PC1 and also into an active phone jack. Follow whatever directions come with it to set up your network connections.
Plug the second usb device into PC2. Plug the phoneline into a second active phone jack. Install whatever software/device drivers required and tell it the info that it is probably going to ask about from the install on PC1 (ip and gateway address at a minimum) Get on PC2 and hopefully have internet access. I sure hope there are good directions with that device bacause it would be very confusing for someone to install if they dont have the required knowledge of networks. Yes you are going to have to read the directions, probably several times unless this is the unusual setup that they actually make the way things should work.
HTH
Dave
