From version 2.2 when you click on Add new deal you will need to select either to add new Person contact, Company contact or to use Existing contact.
To start, click on add contact icon in header on top right side:
In presented dialog you can select either to add New Person, New Company (options you can use to add brand new client in your business) or Add Existing Contact to search your contact base. After selecting an option you will get corresponding section loaded, where you can make an entry. You can add as many contacts as you need, regarding if they are new or existing.
When you select Add Existing Contact, you will get search screen. You can search contact by name, email and phone. After you enter the search criteria press search and select wanted entry from the list:
After that step, contact information will populate in Add Deal screen, where you can continue configuring other information about the deal.