A: The best way is to first add the Organisation onto your account. Then if you have a contact to add on and link up to that Organisation, do that next.
Then create your lead within which you can search for both the Organisation (and the Contact if you have one) and then your saved lead will have the Organisation (and linked contact) embedded within.
Hint: remember that as soon as your new lead is created, you have the opportunity to add tasks relating to that lead. That can help hugely with managing your workflow!