Tap on the little contact guy icon (third tab on the top navigation) to access direct calling options such as dialing a contact directly or dialing a phone number using the MobileDay keypad.
(For this next step you must have already created a new conference service).
To invite people to an impromptu conference call, click on the text bubble to the right of your conference service. This will initiate a text message with a pre-supplied message to your invitees. After you send your text invitation, you will be automatically joined into the call. Recipients will receive a text message with a one-touch link to join your call.