Save Before You Leave The Page
The general rule is that whenever you create new content, such as a page or adding a product, or change site settings, you will need to click on a Save or Update button to save what you have done. These are normally located at the top or bottom of the page. If you navigate away from the page before doing so you will lose that content. Make sure you click to save.
In-line Content Bands
There are some parts of the system, for example product options or delivery charge bands, where Add, Edit or Delete appears at the end of the line. Make sure you click on these BEFORE adding data on the next line to ensure it is saved. If you don't, then you will lose that data.