Hey Jerry,
 
Open the Precision XOC OSD/Monitoring Settings..Select 'GPU temperature' in the 'Select GPU Statistic' dropdown..Select 'GPU1' (or 2 or 3 or 4 for those with more than one GPU) under 'Show in monitor'..Go down to 'Monitor Settings' and type in the 'Maximum value' temperature you desire and select 'Play alarm sound when value is out of range'..The alarm will go off at that temperature..Same with 'Minimum value', which you can leave at 0 or whatever.
 
The Maximum GPU Temperature (in C) as specified by NVIDIA for a GTX 1070 GPU chip is 94 (see Specs), but GPU Boost will begin to throttle your card down at around 83C (pretty sure it's 83C for your card) in order to keep temperature down.
 
Note that the Hardware Monitor (Graphs) must be running (not on Pause) for alarms to be active.
 
For fun: If you don't like/want the stock Alarm sound (that hopefully you'll never hear anyway) that comes with Precision, you can get a .wav file from a multitude of free sources (search free wav sounds, free sound effects) such as WavSource..Download your desired .wav file and rename it to Alarm..Go to the Sound folder in Precision and move (or delete) the existing Alarm file from the folder and replace it with your new Alarm file.