If you get "nothing" from the heater, (ie no fan):
1) Check fuse in power center.
2) Check thermostat (Remove thermostat and connect the heater wire to ground) to see if the heater will start - replace thermostat if it works).
3) Check current limiter located behind grill of furnace. (see photo)
Any further troubleshooting of NO FAN will result in taking the furnace apart and/or electrical troubleshooting with a volt meter.
If this is beyond your capability, you will need to get a technician to help.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW