• Download bp-rate-limit-user-activity.x.x.zip(x.x. is version no. e.g 1.0)
• Extract/Unzip it
• Upload bp-rate-limit-user-activity to wp-content/plugins
• Login to WordPress dashboard and visit Plugins->Installed and activate BuddyPress Rate Limit User Activity
• Now, please visit settings->BuddyPress->Settings or Network Admin->Settings->BuddyPress->settings and Update the limits appropriately
• That's it. enjoy.