Probe confusing

[Amp625]

getting a herpstat T-stat soon to completely switch to UTH and CHE for air temps. I am just usng the T-stat for the UTH. Eveyne sayd something different about whereto put the probe for the T-stat. im a little confused too because i think the T-stat im getting soon only has one probe which is both for a thermometer AND the regular T-stat probe. where should i put and WHY!!!!! i am very confused from some of your answers and appreciate you guys and gals to elaborate a little more. Thanks in advance!!!!!!!