If you're new you should stick to single infusion mashing, which is your saccharifcation rest. This is a good source for reading up/learning:
Generally you want to mash between 148-158. The lower range gives you a thinner, more fermentable beer (lighter bodied), and 158 with yield a beer that has more unfermentable sugars and hence a thick body. These temps are recipe/preference specific. You should read through Palmer's online book for all this information on temps and alpha and beta amylase's.
I'll also add that following instructions that say add water @166 will likely be wrong. This is your strike temp which depends on your house and equipment temps along with grain volume, water volume, type of equipment, etc. This is important because you don't want to miss your desired mash temp. And changing the temp once its in the tun is a PIA. But if your doing BIAB forget this.