Q.cutting back hibiscus
I’ve been told that for Utah winters I need to bring my hibiscus indoors, but I planted it in my garden along a fence line. I’ve been told to cut it down low to the ground but how low? Once it’s cut back, I plan on covering it so it doesn’t freeze, but I’ m pretty clueless when it comes to my favorite flowers. I just don’t want to kill it.

Tropical Hibiscus will not winter over outdoors in your area.
If you have a Rose Of Sharon plant which some refer to as Hardy Hibiscus this will be a perennial in your growing zone.
You will need to determine which type of plant you have.
Here are some links to help you.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/wintering-hibiscus-indoors-winter-care-for-hibiscus.htm