More specifically:
Create a DMR One Frequency system.
Turn ID Search for the system ON.
Create a Site for that system. Add the frequency to the site.
Create a Department for the system.
Create channels as needed under the Department. Make sure you specify both the talkgroup ID and slot for each channel. For example, create an entry for TGID 40 and slot 1 labeled "Lifeguards", and a second entry for TGID 40 and slot 2 labeled "Garbage Trucks". Assign the lifeguard TG entry Service Type Multi-Talk or Other, and the garbage trucks the Service Type Public Works. Avoid the garbage truck channel if you never want to hear them.
With ID Search on, you will be able to see if any other talkgroups are in use, and program them as they show up.