A mac will automatically want to put your photos into the Photos program. But there is a way to over-ride it.

Here is what I do, and if you're trying to do something different, tell us what and we will help.

I download using the built-in download program Image Capture. I download straight into a folder I have prepared in the folder hierarchy I use on my external drive. Then I import them into LR. They never go into Photos unless for some reason I put a few there on purpose. Photos will not let you export directly into LR or Photoshop, so it makes things to complicated for me, I don't use it.

To do something like this you must prevent the mac from using Photos. Here is a link to explain it better than I can http://osxdaily.com/2015/05/31/stop-photos-opening-automatically-mac-os-x/ but do ask more questions as you move along. Lots of mac users here.