If you had looked this up (whether through the forums, or the FAQs) you would have found that there are several forums explaining this. But I will reiterate, since it's obvious you didn't look around:
If you are council in a coven, you can upload spells to that covens spellbook- and thus, the site as a whole. Some covens will automatically promote you to council. Others you have to earn. Regardless, if you cannot do this- you can always mail the council or priest/ess of a coven and ask that they upload the spell in your name. You can also upload that spell to the spell suggestion forum here.