Ok.
I will descibe my work flow:
I will make a categori and then put a product in it.
This is how I do:
I go to Configuration, Products tab, and choose categories.
I click New, fill out the main information.
Upload an image.
Click save and close.
Yes, I created a category.
Now I want to add a product to that category:
I go to Products>Add a product.
I found out, I had to click the product category I just made to bee in the right category when I add a product!
I click New, fill out the main information, type in the price, upload image
Save and close.
All right, allright that seems to work.
Is that the way to do it?