I’m new to arduino and would like to make a few projects with the bare atmega microcontroller but don’t know how to use the 16mhz crystal…
Do I need to use it?
This is the basic circuit I build to use with the ATMega328P. I program the device by connecting to a UNO board with no ATMega in the socket. Has worked with 16, 12 , 8 Mhz crystals provided by Core Electronics and with Ceramic Resonators.
But do you need a crystal ?? No. The ATMega328P can run on an internal 8MHz RC oscillator. To make this happen you need to program the fuse bits. For that you will need a programmer that uses the ICSP interface and programming software designed for that interface. Be very careful in setting the fuse bits as you can easily brick the micro. Nick Gammon has some great web pages explaining all this.
It is indeed possible to use an ATMega controller without a crystal - I have done this a number of times. The Arduino website has some tutorials on how to do this - I used this one when trying this. (Assuming you have another Arduino which you can use to burn the bootloader and program your bare microcontroller.)