Overview
A new customer can be created via the 
Customer Overview Screen
A customer is created via the customer overview screen. To do this, navigate to the customer overview screen and click on the button highlighted in the screenshot.
A create dialogue open to create a new customer.
1. Button to confirm the creation of the customer
2. Button to cancel the creation of the offer
3. You can enter a number on your own or leave it and a number will be added automatically after confirming the creation of the customer
4. You can enter the name of the customer here
5. You can choose a customer group here → 
Customer Groups
6. You can enter the street of the customer here
7. You can enter the city of the customer here
8. You can enter the post code of the customer here
9. You can choose the country of the customer here
Customer Groups
6. You can enter the street of the customer here
7. You can enter the city of the customer here
8. You can enter the post code of the customer here
9. You can choose the country of the customer here
After confirming the creation of the customer you can enter more data for the newly created record as the Customer Details open up automatically