How can I Amplitude Modulate this?
What you have here is a straightforward minimal component crystal oscillator.

Your best bet is going to be to follow it up with an amplitude-modulated amplifier stage, along with the necessary microphone amplifier and signal conditioning.

Best resource will be OLD copies of the ARRL Handbook.  Hit your libraries.

If you can find a copy of DeMaw &amp; Hayward's "Solid State Design for the Radio Amateur", it will give you a lot of help, although not much on AM.  Copies OCCASIONALLY show up on Amazon for reasonable prices.

--de John WB5YOO (Amateur Extra)