Hmm, not too sure - this plant is native to Chile, where it grows in damp woodland, and it prefers soil that doesn't completely dry out. On the other hand, it has linear leaves, which means its adapted to lose as little moisture as possible. From the feeding point of view, shrubs growing in normal garden soil in the ground don't really need much feeding other than maybe a topdressing of Growmore in spring, assuming the soil isn't infertile in the first place.
Personally, I'd observe the usual rules re planting at this time of year, that is, water when the weather is dry until the plant has been in at least a year.

I have this one and treat it the same as any other berberis

Thankyou, B and A. I think I will just proceed as normal. It will be in the ground and I would find it odd not to water it in and water when the ground is dry, like now.