Check out this video for more details:

https://www.youtube.com/watch?v=thjKzwVwGeo&ab_channel=PlonkerJim 

ARK: Survival Evolved - How To Make a Private Server

Playing Ark is so fun, but playing with friends can take your experience to the next level! But what can you do if you are not a fan of multiplayer servers, where everyone can interact with your game and make a mess? You can enjoy your friends’ company by creating a private server, just for you. However, a private server can be a dedicated, or a non-dedicated one. For the first option, you have to possess some serious computer skills or to spend some money, so I strongly suggest trying the non-dedicated one at first. 

How it works: 

• Open the game and select “Host Local” from the main menu. Don’t select “Join Ark”! That will take you to the multiplayer-servers list. 
• Click on the last option of the main column on your screen to host a non-dedicated session
• A pop-up window will. You have to complete the name of the session, a chosen password, and a private starting box
• When you open the map, add in the whitelist the persons that can access your session. Write your friends’ nicknames and share the name of the server