You will obtain Lord Talents whenever your Lord Level increases by 1. You can open the Lord Talent screen by tapping on the Commander portrait at the top left of the screen and then tapping the first icon to the left of your character. Allocate a different number of points to each Talent to attain your desired attribute bonuses.
You can also go to the Maester's Tower and research Maesters' Circle under Commandership to unlock more Talent combination slots. Switch when you need to with just a tap.