Hello Mingyue,
You can copy the NetLogo 6.4.0 folder from the DMG into your Applications folder on your Mac. You can find the Applications folder by opening a new Finder window and clicking on the Applications item in the sidebar. Once you have copied, you can eject the DMG and even delete it. This is how you can get NetLogo installed on your Mac.
Thereafter, you can find the NetLogo icon in Launchpad, find it via Spotlight or even open it from the Applications folder.
Nimesh Neema
Principal Consultant, Perspicacious Solutions Private Limited