Note: you should buy SSL certificate from your hosting provider and ask them to install it for facebook website folder before install facebook template to the server. It's Facebook requirement for each app. Please follow this link to find more details.
1. Create New App
Visit https://developers.facebook.com find App tab and search option to Add New App under My Apps.
Next type an App Name (this can be anything you want, the name you are going to call your tab would be a good choice) in Display Name field and your email in Contact Email field and click the Create App ID button below. Most probably you'll need to complete the Security Check after clicking the Create App ID button.
2. Configure your App
Please go to the Settings tab and choose the Basic submenu.
Now you should scroll the page down and click Add Platform at the bottom.
Page Tab Platform should be chosen.
Please refer to the image below and read the description after it:
Page Tab Image - You can upload the icon for your tab (the dimension should be 111 x 74 pixels, possible file extensions - JPG, GIF, or PNG).
3. Install your new App to your Fan Page