1) install the app
2) create an account
3) provide the account information to your missionary in an email (for me the information is for her to search for my account by the email I used to setup the account)
4) call the Skype test line which should be listed in your Skype account contacts - this allows you to see if you can hear the operator and they also will record you talking and play it back for you which will show if you can be heard by someone on the other end.

I do not know if this Skype test allows you to test the video portion or not...