The official macOS packages are distributed as disk images (.dmg) containing the application bundle. To install Wireshark simply open the disk image and drag Wireshark to your /Applications folder.
In order to capture packets, you must install the “ChmodBPF” launch daemon. You can do so by opening the Install ChmodBPF.pkg file in the Wireshark .dmg or from Wireshark iself by opening → selecting the “Folders” tab, and double-clicking “macOS Extras”.
The installer package includes Wireshark along with ChmodBPF and system path packages. See the included Read me first.html file for more details.