@lukas you may have a look at the guide from Cloudron here: https://docs.cloudron.io/apps/adguard-home/#security
However the setup is pretty simple, go to the DNS Settings in Adguard Home and give some names for your client IDs IMG_0209.jpeg
When you entered ClientIDs the DNS will not be available anymore for anyone who is NOT in your Client IDs list. If you want to update your non static IP from your internet service provider, you could do that and put in your public IP. In that case your local clients can use the DNS even without having a named Client ID
Then you can use the Tab "Setup Guide" in Adguard Home to get guidance how to get your devices configured.
If you want to configure Chrome, Brave or Firefox for DoH you can then use the URL to your Adguard Home DNS Name with appending your ClientId like this for example:
https://DNS-NAME-TO-YOUR-ADGUARDHOME/dns-query/CLIENTID
Please be aware that you should understand what you do and in case of concerns just don't do it. You will be responsible yourself for anything you do.