First of all, you have to go to the search bar and type Snapchat then hit enter and select the first option that appears on your screen.
Install the official Snapchat app.
Once you have completed the installation then open the application.
Your Snapchat app will open in a new tab right with the blue stack.
This will look similar to what you use on your mobile phones.
Then log in to your account enter all your details which they asked for. Your user name, email, passwords, etc.