Well, there is a website dedicated to this! It illustrates the process:
Here are the steps from that site in a nutshell:
You have to remain seated for the whole wiping process. Start out with a decent size wad of tissues, three balled-up squares should be enough. Reach around and behind your butt, and lean into the opposing cheek. Start wiping with the pointer, middle and ring fingers. Use moderate pressure and wipe at a cautious speed from front to back. Repeat this step with the same amount of tissue until the amount of remnants on the paper decreases by fifty percent.
For the second step, the amount of tissues should be reduced. Two crumbled squares should be enough at this stage. Follow the same directions of step 1 (with the reduced paper amount) but using more pressure with each wipe. Continue until the amount of remnant on the tissue decreases to a small amount.
The paper in the step should be decreased to one folded square. This really is sufficient. Repeat the same direction from step 1, but now you should be using significant pressure. As you pass over your anus, relax the sphincter and slightly press the pad of your middle finger into the opening, continue the progression from front to back. Repeat this step until there is very little to no remnants transferring onto the paper.
The final step which is often ignored, is to use a wet wipe, repeat step 3 until absolutely no remnants remain. This step is to ensure fresh, thorough clean that is second only to a bath or shower. This will reduce any staining, odor or itching that may occur later.
Flush, adjust your clothing, wash your hands with soap and water.
Also, this video explains it well.
A tip for your friend, always take a bottle of water when using a toilet with toilet paper only. This way things will be easier and much more like home.