To register new suppliers we will go to:

Finance → Purchases and Suppliers → Suppliers.

It will open a window with the list of all suppliers that we have discharge. To be able to register a new one we will click on the "New" button as shown in the image provided.

Once we have the tab of the provider, we will fill it with all the necessary data and that we have of that provider. We will click on the "insert" button and we will have it created.