Chromebook

I have been trying to help my brother get his pictures to his Chromebook computer.   I think he has a I Phone, but am not sure.  Whatever he has, many picture "stored" on his cellphone.
It it were pictures stored on his phone to Windows, I can do that, but Chromebook and Possibly Iphone are different.
What would be the best way to get his pictures to his computer.
If it is an Iphone, is there away to access the picture that our stored on the Iphone System.  I believe there is a way to access the online system from an android phone but I do not know how to access.
I am quite literate in Windows, but not the cellphone/chromebook systems.