If alerts are enabled on the Ushahidi site you are using then you will be able to subscribe to them by going to http://example.com/alerts 

Once there you will have the option to select the area and radius of interest as well as report categories that you wish to receive alerts on. 

Subscribing to reports does not require an account on the Ushahidi system, but if you subscribe to reports without using an account you will not be able to remove your account from the system. 

If you do have an account, when you visit http://example.com/alerts after logging in, all alerts that you subscribe to will be listed at http://example.com/members/alerts. http://example.com/members/alerts will show you the alert latitude and longitude along with the radius size and categories associated with it.  It will not list numbers or email addresses associated with the alert.  You can register for multiple alerts with different phone numbers and email addresses.