Adding New Fields to Listing Manager

Hi, I hoped to use this plugin to list caravans and motorhomes, and so I’d need to add various new detail fields such as, Berths, Internal Length, Awning Size, and so on…
Is there documentation that could teach me how to achieve this?

Also, as I’m in the UK I’d have to change “Highway MPG” to “Motorway MPG” and have the option not to show it if showing a caravan.

Documentation would be good, I look forward to hearing from you.

many thanks