Three types of files in mac can install
Determine what you have. If you have a file ending in dmg you have a disk image. If it ends in zip then you have a compressed file. If it ends in pkg you have a package file. There are other ways of bundling applications but these are the most common.
Uncompress, mount, or execute the given file. The methods below show how to perform each of the tasks depending on the given file.
Type 1 : DISK Images
Disk images have a .dmg extension and can be mounted as removable drives.
Double Click on the disk image and it should mount the image and open a new window with its contents.
A drive appears with your contents. Look through the given files to find the application.
Type 2 :Compressed files
Uncompress the file. If you have a file that ends in .zip you only have to double-click on the file and OSX will uncompress it into a new folder.
Open the new folder to find the application.
Type 3: Package Files
If an application needs to make changes to the system in order to run (add fonts, preference panes, services, helper modules, etc.) than it may be distributed as a package file, with a .pkg extension.
Double-click on the package. This will launch an installation wizard for the application. The installation wizard will perform all the necessary tasks to correctly install the application. Once the installation wizard has finished the application will typically be found in the Applications folder, ready to run.