Setting up Lightroom on external HD on a new Mac

I've been using CC for around 18 months now and I'm very happy with it.

I've just bought a new Mac and CC has installed flawlessly. All my images are available and everything is working perfectly.

I have just one issue; On my old computer, I stored the full-res versions of my images (around 350gb worth) on an external HD. I'd like to keep using this drive but I dont know the correct way to set this up.

If I simply go to Preferences and point CC at the local drive will it just recogonise the previous files, or will it attempt to download and save my entire library?

Thanks (in advance) for your help.

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