Just starting.

[tagra912]

Can I use  an external hard drive to store my LR photos on? Only have a 222 GB hard drive and lots of GB's of photo and catagories to put in catalog.

[SeanMcCormack]

Yes, absolutely. 

Choose the drive in the Destination panel of Import and go from there. 

For example, here's my external drive selected for importing photos. 

[tagra912]

Thank you. A further question. If I put my photos on the external HD  and for some reason need to move the external to my other computer, I use one for business and the other for things like FB, can I just replug the external back into the main business computerwithout losing anything as long as I keep the photos in the same place on my external?

[dj_paige]

Thank you. A further question. If I put my photos on the external HD  and for some reason need to move the external to my other computer, I use one for business and the other for things like FB, can I just replug the external back into the main business computerwithout losing anything as long as I keep the photos in the same place on my external?

By @tagra912

Yes, except that on Windows, if you unplug a drive and plug it in again later, sometimes the drive letter can change. This would cause LrC to think the photos are missing, you would have to tell Windows the change the drive letter back to what it was previously.

To prevent this from happening, you can assign a letter to the drive at the end of the alphabet, such as Y or X or W or Z, make sure LrC is reconnected to photos on Y (or whatever letter you choose, see Figure 4 here) and then un-plugging and re-plugging in the drive should not cause a problem.