"Remote unmoderated usability testing is so fast and easy that some teams make it their only evaluation method. But don’t shy away from its more robust alternative, the remote moderated usability test, which can give you more information and is also inexpensive." as Kate Meyer and Kara Pernice from Nielsen Norman Group point out in their article.
When you plan a study you have to choose an appropriate tool for communicating with the participant and plan the tasks that have to be done by the participant (as in a normal usability test). If needed and if possible you should practice the tool you and especially the tested user will use in advance to avoid problems during the test session. Don't forget to send out reminders to all participants. The procedure of the test itself is quite similar to any other test.
You find a more detailed explanation and description on how to conduct the testing session in the original link.
Anything to improve with the method description? Just send an e-mail with your suggestion. Thank you!