what exactly you want to know? For using H bridge, at any time drive diagonally opposite MOSFET's and other two mosfets should be off. The switch should occur between mosfet pairs when half cycle completes.
As far as code writing goes, C is simpler, follow any of these scenarios.
1. SWPM with complementary PWM output using ECCP/COG/CWG/standalone PWM module and drive the complementary PWM output to diagonally opposite MOSFET's, while other two are switched OFF.
2. PIC16F876A does not ECCP, so instead switch one of either high side or low side mosfet is permanently on for half cycle and other fed with PWM and change mosfet for next half cycle.
I hope, i answered the question, if not plz let me know with the exact question.