Location: Unlocking this side-mission, connected with the Epsilonist cult, is obvious and you do not need to prepare yourself for it in any way, or wait until you reach the appropriate moment in the campaign mode.. While playing as Michael, connect to the internet in any way you want (e.g. using your smartphone) and use the search engine to find the www.epsilonprogam.com site (the above screenshot).
After you access the site, find the Evaluate Your Identity button. The test consists of 10 questions, where the answers you provide influence only as much as the looks of the site that presents the results. This will not influence, on the other hand, on the unlocking of the mission because it will become available irrespective of the options that you have taken while taking the test.
Wait for a question mark to appear on the map, which is going to take you to Raton Canyon in the central part of the map. Get there and approach the red pick-up truck, which will start a cutscene and complete the first meeting with the Epsilonists.
Rewards for the completion of the mission: none
Requirements for the completion of the mission in 100%: There are no additional requirements for this mission so, it gets completed in 100% automatically.