Create click track

You can use a soft-synth like TTS-1. Pick a drum or percussion sound and create a 1-measure midi clip with quarter notes. Then you can bounce to audio, copy and paste, or turn into a groove-clip, and drag it out as far as needed.

I don't use the metronome, but instead prefer to create a simple drum track via the step sequencer.
 
Just insert any synth capable of producing percussion sounds - TTS-1 is an excellent choice for this. You can make this an Instrument Track or separate MIDI and audio tracks (I prefer the latter). Once you have done this, you'll be able to select the MIDI track and then bring up the Step Sequencer. From there it's a simple matter of figuring out how to work the step sequencer, which is pretty easy and you'll figure it out in a couple minutes. The resultant MIDI data will be in the form of a groove clip that you can either loop while recording or stretch out to the length of the song.
 
I like this method better because I can program a beat that reflects the feel of the song, rather than the steady click-click-click of the metronome. Drummers in particular seem to have difficulty playing to a metronome, but have an easier time with a simple drum pattern. The pattern needn't be complicated; kick, snare and hi-hat are all you need.