Generally just a selection on the t-stat. You're t-stat should have a furnace, AND heat pump selection. Very possible it's got the wrong t-stat, or it doesn't really have a heat pump. I'd guess they put the wrong t-stat in. Some, like in our previous motorhomes, do work in conjunction with the furnace, but they still have both selections on the t-stat. If it senses it's too cold (can't remember temp), it'll kick the furnace on to catch up along with the heat pump, then furnace will shut off when it gets to a certain temp and heat pump will continue. Not all are configured like this. One thing to remember if you didn't already know, is once you get down to say 40° or so, the heat pump is worthless. You'll get nothing but cold air. Above that, they're great. We've had both set ups, and this time again opted for heat strips for this reason since they don't care what the outside temp is.
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.