What is the easiest way to connect a breadboard to a multimeter?

Use alligator clips for your DMM test leads and pin it on the leads of your breadboard wires ( terminals) where you want to test.

Please see the below picture to understand what I am trying to say.

Please for heaven's sake don't try forcing those test lead pins into the breadboard holes, they damage the copper strip inside (personal experience.)

You could either make some leads up, with banana jack on one end (available from any decent electronics vendor) and header pin, crocodile clip, or similar on the other.

Or do what I have done many times and just grab a bit of solid core wire (of a size suitable from breadboard), strip at both ends, wrap one end a few times around the test probe with needle nose pliers and stick the other end in the breadboard.

You can also buy accessories that plug onto the end of your test lead probes which provide a little grabber for attaching to small component leads and jumper wires etc.

Of course, a short bit of bare wire twisted round the probe is a lot lot cheaper :-)