Make a comfortable village.
Food and water.
Houses with beds for everyone (a native house with leaf beds is fine too).
Make sure everybody in a group has compatible personalities.
One man per group of women (or they'll get competitive).
Toilets for men without a harem. (they aren't really toilets).
Hit them with weapons with "faint" property. If you're controlling the male MC and NPC is female, raping them with R button and a lot of clicking also works.
The game uses WASD (movement), Q (for dancing), E (context-sensitive), F (heavy attack), R (wrestling), left and right mouse buttons.