Engineer here, who has learned marketing and sales on the job.

Marketing in 1-to-many. Sales is 1-to-1. So sales generally only makes sense in the context of B2B, not if you are selling $30 B2C software.

Sales isn't that hard (afterall sales people can do it!). Talk to the right people, find out what they want, ask for the sale (if appropriate). Don't take it personally if they don't buy.