You then need to type in 'visitors' into the search field. You could also type in 'top stalker' into that search box. Then just press enter and a list of applications will appear. It's down to you to decide which application you want to use. Just choose an application that has a description which fits your needs. You then need to click on the application's title to be able to view the application's details. Then you need to click 'Go to app' which is found at the top of the page.
You will be prompted to click the 'Allow' button, which will accept the application and install it onto your Facebook profile and account. The directions of how to use the application will appear on your browser once you have gone about installing it onto your Facebook profile.
So how do these applications work if they have no way of knowing who has been looking at your profile? They do something similar, which is possible. The applications track the amount of comments and likes that all your friends have made on your profile within a given time frame, and tell you that your 'top stalker' or 'top viewer' is the person that likes and comments the most on your profile. It's just a little bit of fun and is not a way of knowing which friends views your profile the most, as there is literally no way of an application being able to know this.