Someone talk me through lowering humidity in house?

Get a cheap hygrometer first so you know the number. Somewhere around 30-50% is the usual target. Then the boring stuff that does most of the work: run the bathroom fan during and for 20 minutes after a shower, use the range hood when cooking, make sure the dryer vents outside, and don't dry laundry on racks indoors. AC pulls moisture out too, as long as it's sized right. If it's still high after all that, a dehumidifier in the dampest room (often the basement) is the next step. Check the gutters and downspouts as well, water dumped next to the foundation ends up inside.