Becoming a GM is easy - simply open your Settings from your Dashboard (wrench icon) and set yourself as a Game Master. Once you do this, a GM Screen option will appear on your Dashboard.
The GM Screen allows you to run Rollplay sessions of your own. As GM, you will be the arbiter of the action. Remember that you always have the final say. You are free to fudge or even disregard the die results if the situation warrants.
At the bottom of the NPCs section, you can enter an NPC's name and use the Add button to add them to the session. The added NPC will then appear in a list on the left side of the section. NPCs begin with a status of Hidden, which means the players in your session can't see them. You can set their status to any of the standard injury levels for them to appear to players. Finally, you can click the X by an NPC's entry in the list to remove that NPC from the session.
Clicking on an NPC in the list will display its stats in the lighter colored panel on the right side (when you add an NPC, it will be selected automatically for this). On that panel, you can set the NPC's stats. These stats are much simpler than what player characters use, because Rollplay only needs to know their combat capabilities.
At the bottom of the Players section, you can enter a player's name and use the Add button to add them to the session. Alternatively, if you're not sure how to spell a character's name, you can use the ? button to search by player name. Like NPCs, you can set players' injury status or use the X to remove them from the session.
Additionally, summoned creatures will display below the player that owns them. Like players, you can set their injury status or use the X button to force them to unsummon.
Clicking on a player in the list will display their stat printout in the lighter colored panel on the right side (when you add a player, it will be selected automatically for this). On that panel, there is also a link to view that character's description. Underneath the panel, transformation options will appear if the character has a supernatural type that's capable of it - you can force the player to start or end a transformation.
This panel shows you the events that have transpired so far in the Rollplay session. Compared to the player's Rollplay session screen, you can see more information here. Events that only the GM can see will be shown with a darker background.
Additionally, many events will require you to make a determination of their success. This will be done with buttons that appear directly on the event.
These are your main controls for running a session. At the top, you will find a dropdown for selecting an NPC. This selection will choose which NPC to use for anything that doesn't have its own specialized selection. Also here is a comment field that will be used for all of the rolls on this panel.
When you send a roll to a player, keep in mind that it may take some time for them to make their roll. If you send a roll to a player who is currently using the Rolling Popup to perform another roll, you will be notified that the roll is queued for when the player is ready. Most queued rolls can be canceled, if they have been sent in error.
Make sure you pay attention to the events that are coming into the Session History. Many of them require input from you before they can "complete". Ideally, you shouldn't leave any events unresolved in the Session History feed.
Special care should be taken when processing attack rolls. When you determine whether the attack roll succeeds, or fails, you will also need to use the in-game description of the attack to determine the damage type. Be sure to set the appropriate type here so it interacts with damage resistance/weakness correctly.