How long to I initially charge my new IPhone 6?

How long to I initially charge my new IPhone 6? - 1

Until it's fully charged.

As much or as little as you want. It makes no difference to the total lifespan of the battery.

Those worries relate to the obsolete NiCad rechargeable batteries which could suffer "memory effect" if not fully charged to begin with and then regularly recharged before they were almost totally exhausted.

Modern lithium polymer batteries don't have the same problems; charge them as much or as little as you wish for as long or short as you want. All that matters is that you have enough charge to last until you can next recharge.

You don't have to charge it initially if you don't want to. It usually comes with about a 50% charge. In the old days, the types of batteries in phones required that you charge them first, but that's no longer necessary with new Li-Po batteries now used in phones.