To enable quotes, go to Setup, then do a search for "quotes" (remember, don't hit enter when searching -- it's just easier). Find and click "Quote Settings". Note: on the image below, you'll notice a lot of other options for quotes. These are only available if enabled.
On the next screen, enable the quotes and save it.
Once enabled, you'll notice that quotes are now an option on the opportunity, working much like opportunity products. These quotes allow for printing (through templates) and allow for the revenue to be calculated based on the products added to the quote.
We'll explore more of quoting such as template creation in future tips (but may expand on this on our monthly webinar where we demonstrate our tips.