In the login screen, you will need to enter your email address and password.

Once you have logged in, you can verify the store's configuration. For this, go to Menu →Account Settings on the lower left:

And in account settings, click on “Refresh Store Settings” to verify the data. If any configuration needs to be changed, you can use the pricebook app to make the changes and then “Refresh Store Settings”:

When you scan an item, there are a few things that will happen:
If you already have a price assigned to this item, it will be automatically added to the cart
If you have not set a price yet, we’ll get it from our database of 100k+ skus. You will only need to add the price:

We might also ask for verification of the item data:

If it's a new item, or the item does not match, then you can choose from one of the manual and set a price:

To edit an item, you can simply tap on it and it will open on the screen. Here, you can edit the quantity and price of the item:
If Price Override is enabled, then you will be able to choose if the changes are to be updated in the Pricebook or not: