[Elecraft] New to Ham, 3, group, with a question RE: Reference Oscillator TCXO

[Michael Gillen via Elecraft]

Hello all, new to Ham (about two months) and just built my K3 over the weekend. Wow that thing is complicated. I came from using a Kenwood TS-440ASAT for the past 6 weeks so a lot to learn.
I'm a bit confused about the TCXO and especially how to perform the calibration of it and would the upgrade to either the KTCXO3-1  TCXO  1 PPM or K3EXREF be a better choice?
My guess on what the TCXO does is provide a stable clock to the synthesizer. Is that correct? And the more accurate/stable the better (hence the upgrade paths)?
So I have the "standard" TCXO right now. I get lost on the instructions after step two which is to tune to WWV 20MHz. I don't understand whats going on to "SPOT" the sidetone etc. If there's a video on how to do this that would help a lot.
Thanks and 73!MichaelKK6RWK