Whenever you are looking for a contact Sellf will look for you in the address book and automatically import it, if you have not already done previously. If the contact has the detail "company" compiled, Sellf will create a company contact automatically.
If you do not see your contacts in Sellf, go in Sellf settings (click on your picture on the left) and activate the "Access to contacts"
Sellf reads your phonebook but don't change them. This means that if you change the information of your contacts in Sellf, these changes will not take back in the address book and vice versa.
You can activate the "Save contacts in the address book" feature if you want to create your new contacts in Sellf and make sure to be saved automatically in the address book. This step will be made only when you create for the time the contact, further changes will not be saved.