First you need a blaster. You’ll get this as a gift from Bode when you visit Jedha for the first time. Then, you need to purchase the Point Blank skill from the Blaster Stance skill tree, which will require a fair few Skill Points. As soon as you’ve added Point Blank to your arsenal, ensure you have the Blaster Stance equipped at a Meditation Point, then use it to defeat ten enemies. You’ll need to essentially parry a weak enemy with a press of Y at the right moment for a Point Blank kill - it’s tricky, so it might take a little while to work out the timing. Stick with it, and this will pop soon enough.