Sales is about applied knowledge. There are a ton of great books, many of them previously listed. A couple that have recently read, that really resonated, were "The Challenger Sale" and Dan Pink's "To Sell is Human".

Read, then apply, then read again, and re-apply. Put yourself out there, understand rejection is not personal, rather a chance to improve. Anyone can be a great salesperson if they approach it like learning any other skill. Good luck!