Hello @linhd
If you’re only using the standard columns that ship with StaffList, there won’t be a column for your staff images. So it’s advised that you modify your spreadsheet to add a new column where the image URLs will be recorded (and later, imported). Once you import your spreadsheet, the column will be available for individual edits/updates from the StaffList administration page.
To your second question: we advise you to re-import your staff from spreadsheet. If you don’t have a spreadsheet created, you’ll need to make one, unfortunately. It’s also possible, if you have direct access to your database (via a tool like PHPMyAdmin), you make the adjustments to the table directly — but we don’t advise this approach, as it can be damaging to your website if you do it improperly.
Regarding format, JPG or PNG will do nicely.
You’re given CSS classes to fine-tune how your images will appear both in the StaffList table and the tooltip. So your image resolution will depend on how you ultimately wish for the images to be viewed on your web site.
ERA404