DMR-MARC is an organization which requires registration and thus allows you access to a group of DMR ham radio repeaters. The DMR-MARC organization is the best known group, and perhaps only group, that coordinates worldwide Amateur Radio DMR Subscriber ID’s. Although there are alternatives, this seems to be the largest and most widely known way to get on the air with your MotoTRBO or other DMR compatible ham radio. Consider DMR-MARC the current "master listing" of DMR repeaters worldwide.
DMR-MARC: The Motorola Amateur Radio Club TRBO DMR Network
All radios on ham radio DMR networks require a unique Subscriber ID. Each radio has a unique Subscriber ID. A single ham operator may have multiple DMR radios, each having a subscriber ID, thus allowing one ham to have multiple subscriber IDs.
The DMR radio needs to be programmed with data to allow access onto this DMR network.
You can use one of the various online DMR repeater network maps to locate information for the repeaters in your area.
You can use a preconfigured "codeplug" for your make and model of DMR radio that will get you on the air in your area faster than manually programming the radio yourself. Programming DMR is a lot more involved than a standard analog FM radio. You should search online for "codeplug" or "code plug" as it is sometimes used with or without a space. Make sure the one you select for your area is for your specific radio.