BTW - this should be posted under "HELP" forums, not parts talk, as you aren't discussing a specific part !
Do you have a full kit ? Like a GReddy / HKS / Blitz ? Or just a gauge that says "TEMP" on it and you have to figure out the rest yourself ?
Need more info to actually help. Don't forget to run a search on this site for exactly that phrase as well, your answer could be already here.