Apple does something VERY weird here, they've "captured" all of the images into a storage section of the Photos App itself. There's no way for LR or any other application to access them.
HOWEVER: if you export them from Photos, you're good. Needless to say, you do have to make a choice though as to how you will export them.
Open Photos. If you have images that are already sorted in groups (e.g., events, travel locations, family, whatever. Select that group. Then go to File (menu)-> Export and then you have to make a decision:
If you export the photos, the top choice, any and all changes you made will be permanent, you can then import them into Lightroom.
If you select Unmodified Original, than the images will be exported without any of the changes you made. The advantage of this is that LRC can do a much better job of adjustments than Photos can but more importantly, as you get better with LRC, you will discover better ways to improve images. If you lock in your adjustments from Photos, some of those adjustments will no longer be available to you because you do not have access to the original images.
Obviously the other disadvantage is that you will have to make your adjustments all over again. The advantage is that the enhancements that you make in LRC will be better AND you will always have control on how they look.
FWIW, my choice is the latter.
Anyhow, after you've exported that block and imported them in LR, than you can start on the next block. Unfortunately there is no real fast easy process for this. When you do your imports into LRC, please read up on things that you can do to speed the process up for Keywording, Presets and other features built into LRC. One good place to see/find this is at Lightroomqueen.com. If you register with her, you can access a free PDF that gives excellent basics on all flavors of Lightroom.