To get into the backend of your WordPress site you are going to want to get to your WordPress login screen. It will be your domain name followed by “wp-admin.” If your domain is xyz.com then you will go to xyz.com/wp-admin. Here you will put your username and password.
Recommendation: Setup your username to be something different than “admin.” This will help protect you against hackers logging into your WordPress backoffice. “Admin” is the default username and you can change this when you initially setup your website.