Can't change pins in AM2320 code, types mismatch
Two problems:

When you create an object instance with no parameters you must not have parentheses. You should construct thus:

TwoWire mywire;


The constructor expects a pointer to an object, not an object. Just take the address of the object with &amp; and pass that:

Adafruit_AM2320 am2320 = Adafruit_AM2320(&amp;mywire, -1, -1); // as the default values

However
Most Arduino boards have the I2C pins hard-wired internal to the chip and can't be changed. You would need to use some form of software implementation that is also a polymorphic child of the TwoWire class. If such a thing exists.