In space combat with an unmodified user interface, you'll have a section of the screen with your Bridge Officers listed with their abilities below their portraits.

Above that is a one line bar filled with abilities, it should be blue and again if unchanged from stock settings it will be as described.

That is your "abilities bar" and you can use it to select various skills and abilities.

Now that you know where that is pres "p" on your keyboard.

This will bring up a list of various skills and abilities that your character can use in space combat.

Scroll through them and select the "grappler" ability, drag and drop this onto the previously mentioned "abilities bar".

"powers" Hit the P key and drag to your bars.

Dang ninjas, swear I'm going to make a pirate to kick their.........