From Sales / Customer.

Right click anywhere within the left hand grid.

Select "Add New Customer"

Fill in The Customer Type and Customer Name.

Then click save.

Once you hit save you will be able to enter Addresses and Phone Numbers

You can also add a new customer directly within the Dispatch Add/Edit job screen.

If you click on the drill icon in the Customer Name field and select the green plus sign it will bring you to the new customer information screen.  Follow the instructions as above.