hi @jbfa, it's pretty simple - you just send the amount of STEEM or SBD that you want to use to promote your post to one of the bot accounts with a link to your post as the memo.

If you're new to the process I suggest using the Steem Bot Tracker Website and sending only to bots that have the green auto-refund icon. Those bots will automatically refund your money if you do anything wrong so they are good for beginners.

Let me know if you have any more questions!