I found that Dropbox is the best method for my syncing photos between my Android phone & my iMac …
Just download/install
Dropbox (free) on both then turn on download to computer on the phone, it's pretty straight forward …
I have my phone set to automatically download from my phone to my iMac using my home WiFi set-up.
Any photo I take either at home or when I'm out and about then appears in the Dropbox Camera Upload photo folder on my Mac if I'm within the home network range … it's very convenient.
You can also set it to upload/download using a data plan but I'm skint so I never choose that option
The long way is to connect via USB, mounting the phone on the desktop in Drive Mode then navigating to the DCIM folder where your photos lie & dragging them onto the Mac's desktop.