Please note this option is available for products you have manually created already.
Step 1: Log into Client Manager
Step 2: Go to Menu > Portfolio > Products > Select Products Tab
Step 3: Select the product you want to make adjustments to by clicking on the View icon next to it.
Step 4: The Product will open in a new browser tab.
Scroll down to Product price history and click 'ADD PRICE' as per below: