Can I Read How Many Amps Are Being Used W/ A Multimeter?

Depends on what you are looking for.
If you are trying to find a parasitic type load then start at the 12 volt DC power distribution panel. Most parasitic would or should be under the 10 amp.
If you are trying to determine how much you are using normally then connection on the main battery cable would be best, then pull each fuse in the dc panel to see what loads are on that circuit.
If there is enough slack in your DC panel you could connect there, but may not be able to connect to the feed into the DC panel.