You install BuddyPress like you would any other plugin. If you need asisstance with installing WordPress plugins please see our article on installing WordPress Plugins.
Go to the plugins page within your WordPress Dashboard and search for "buddypress." Install the plugin as in the example below (it shows up first however it may be different for you)
Once the plugin installs, activate the plugin. When the plugin is activated, you'll now be able to configure BuddyPress.
If you need further assistance please feel free to contact our support department.