Dec 31, · Invite People to Sign Up Once you have completed your sign up and clicked the Publish button, there are several options for sharing your sign up and sending invitations to your group. Once you have published the sign up, the Publish tab becomes the Share tab. Tap Invite people. Enter the email addresses of people that you want to invite, or tap Invite from Contacts to select people saved to your device. Tap Send. Note: It's not currently possible to invite guests from Slack's mobile apps. Open the Slack app. From the Home tab, swipe right to open the main menu. Tap Invite people. Since Graph API v, /me/friends returns a person's friends who also use the app. You may use the Requests Dialog to invite people to play a game. However, if you want to build a custom multi-friend selector within your game, you need to use call /me/invitable_friends which returns a ranked list of a person's friends who do not play the game, along with a token which can be passed to the.