When to pitch nutrients, which nutrients to use, and how much is rather lengthy. Therefore I will direct you towards chapter 10 of the newbie guide:
http://www.gotmead.com/forum/attachment.php?attachmentid=1300&d=1395107426
Although, I'd be careful with the phrase "Using nutrients is not an absolute necessity", especially in a newbie guide. It takes quite a bit of experience or specific recipes (JAOM) to avoid the use of nutrients. My personal short answer would be: I pitch nutrients around two hours after I pitch the yeast so that it's during the lag phase. EXTRA: I think the absolute latest to add nutrients/aerate is the 1/2 sugar break, but you might want to aim for the 1/3 sugar break
- I wouldn't pitch the nutrients while the must is still hot as this may be detrimental to the vitamins present. There is some discussion on whether or not to boil in general, and it seems the majority agree that you usually can do without boiling in most cases (and would possibly be better off).
- You can also check up upon staggered nutrient additions (SNA) for a more "advanced" read. This is optional in many ferments, but SNA is never bad.
- Needing a yeast starter is also a possibility, but I never used a starter with my dry yeasts