You can manage and add suppliers in 'Products/Product settings/Suppliers'.

Managing suppliers is useful to track your sales by supplier, and helps streamline your ordering process. When you create a stock order, you must linked it to a supplier.

For each supplier, if you click on the wrench icon you can add contact information.

To assign a supplier to a product, go to the product form and select the supplier in the Supplier drop-down menu.
You can only attach one supplier to a product. If you are ordering the product from multiple suppliers, the product inventory will be always assigned to the selected supplier.

You cannot delete a supplier if he is linked to some products or to stock orders.
But you can hide your supplier by switching off the active button.
If your supplier is inactive, he will not appear in the product search settings.
Reports will continue to display hidden suppliers if some products sold are linked to them.

You can import in bulk your suppliers in 'Products/Import-export/Import data: Product settings'.