Go to the menu Rates and selections New rate. All items will appear by category. Enter in the top menu the Name of the new rate and select whether prices include taxes or not. Also, at the same level, you can select the item family that will be shown below.

Enter a price for each item. If multiple items have the same price, you can select the checkboxes at the beginning of each item's line, then click the price box, to add the same price for all selected items.

If you already have a rate created, when you want to add a new one, you can choose whether to copy the items from another rate and whether to increase or decrease prices by a percentage or amount. This way, it won't be necessary to recreate all the items manually.