Regulating voltage so USB works with module
Find a data sheet for that thing and figure out what Vchg is all about.
Find a data sheet for that thing and find out how much current it needs when operating.  Most especially the maximum current it needs when the GSM module is transmitting.
If it needs more than 100mA, then don't count on using it with USB power.
Use a 3.3V regulator to drop the 5V from USB to a voltage that both the GPS and GSM pins will accept.


3.3V regulators can be had as linear that you can use with minimal parts on a PCB that you make yourself.  You can also get 3.3V switching regulators that are more efficient but more complicated to build.  You can get complete modules for both types of regulators.

In response to comment:

You will NOT be operating that thing off of USB power.

The datasheer you linked to in the comment includes suggested circuits for the voltage regulator, and mentions that the GSM module draws up to 2A when transmitting.  It also recommends using 4.1V, which is comaptible with both the GPS and the GSM parts.

So, USB is right straight OUT.



USB is only supposed to supply up to 100mA until the USB host (in the PC) has negotiated with the device via data communication, at which point you can only draw upto 500mA.  Since you won't be doing any data communication, you can only count on 100mA.  Despite this, you will often get 500mA because some (many or most?) host manufacturers just ignore the specifications and supply full current to all devices.  It just may not work on some USB ports.