There are two reasons you may need to invite photographers to an event.
You're an event organiser and wish to invite photographers (you know) to cover your event.
You're a photographer and need help to cover an event.
Login to GeoSnapShot.
On the dashboard click on "my events".
A list of your upcoming events will appear. Click "manage" for the event you wish to invite photographers to.
All the details of your event will appear. Click on "photographers".
Enter the email address of the photographer you would like to invite.
They will receive an email invitation to attend and shoot as well as all the information about the event.
Once you have sent the invite, click on "photographers". You will see that the photographer you have invited is now on your list. The current status will show "invited", but this will change to "declined" or "accepted" once they have notified you of their decision.
There is also an option to allow any photographer to upload photos to your event. If you wish to activate this function, select the access control box shown below.
Here's a quick 1 min video running through the same process :)