Here's a video on how to obtain ALL of the prologue achievements, and more! Links to the specific achievements, in order of when you'll obtain them, are in the video description. I didn't show battles as some are walked through by the AI, and most others are simply auto fought and won. The last one appears very difficult, but my game cut out, and I didn't complete the prologue.
As for this achievement:
1. Late in the prologue, after the quest mission, you unlock the ability to recruit Lords.
2. Do this right away, and you shouldn't have an issue.
3. If you need help, click on your base first.
4. Then click the Lord option that is in the bottom middle of the screen, as the farthest right option.
5. Pick one of the Lords to recruit, any Lord!