Purchase the War Child Charity DLC then start the game. Note: There are three prices for this DLC on the store page, however they all feature the same content.
Easy start
Each a game is started, you will receive new characters as well as new items in your house. Explore your house quickly and begin reconstruction as well as heal anyone that is sick. Build as much as possible with your available resources to avoid losing them during the first raid. Balance your time between fixing the house and building new things. It must be repaired before winter starts.
Fights
Optimally you will avoid fights, but you will eventually end up in one. Use a combination of stealth and melee weapons. Hide and wait for an enemy to pass. When the icon becomes yellow, take them out with stealth or sneak up on them before killing them. If you are not outnumbered, consider luring them into better areas for a kill. Run around to make some noise to bring them to your position. Hide in the shadows then use stealth to kill them.
Resources
When sending a survivor to scavenge, have them equipped with the largest backpack available. If there are multiple people with the same backpack space, send the best runner or the soldier if available. You must leave before 5 a.m. or you will risk losing your survivor. Consider leaving at 4 a.m. if the exit is close or at 3 a.m. if there is a lot of distance to cover. Carry equipment that is useful for scavenging. Although it will occupy space, it will save time. Food is your most important resource. Always carry it with you. Return with components, wood, and medicine. Take items and explore with them, then replace them if you find rarer and better items. Never return with empty space in the backpack. Explore for resources by starting at the safest areas first. Check the description and ignore those that do not have any food. Search everything when an eye symbol appears to get a chance to find hidden items. Because the CPU also scavenges, begin with less risky areas to avoid losing your gains. Consider building stockpiles of items closer to the exit. This usually works, but carries the risk of someone stealing all your resources. Use stealth while scavenging but be ready to kill enemies. For example, send Roman if he is available, do a clean wipe of an area, then get as much as you can during the first night. Follow up by sending somebody with a larger backpack during the other night.
Survivors
Feed survivors only just enough to keep them alive due to the scarcity of food. Only feed them every other day. Save your extra food for times when it becomes scarce. Because survivors do not sleep overnight, when things are dangerous, put them on guard duty during that time and rest them during the day. The more people you have defending, the better. If possible, give them weapons to increase their stats. As day breaks, send tired survivors to sleep and send one of them to craft. Switch jobs as soon as one is up to always have rested survivors. The characters and items you are given affect your chance at survival. If you have characters with no vices, try the items used for vices to get some deals. Build your base at the bottom of the house and try to place as many survivors in one place as possible to reduce the distance that has to be covered by them during the day.