Hi Edbert,

Welcome aboard the cruiser Odoo. Enjoy your trip. )

I think, it would be good for you to start from the text documentation.
And also especially from the video tutorials.

It needs time. But it is really helpful.

You can find text and video tutorials using the menu of the odoo.com website:
Community > Learn > Tutorials and Documentation

Advise you to go through the video tutorials with quizzes:

• Accounting
• Sales
• Inventory
• Purchase
• and maybe MRP, if your business includes manufacturing.

You can also read more about loading goods in the text documentation:

Community > Documentation > User Docs > Miscellaneous > Export and import data.

And finally you also can find an Odoo certified partner, who will step by step implement the Odoo system in your business.

To find them you should to go in the main menu:

Community > Find a Partner 

So wish you enjoy Odoo,
Vlad Odooer )