Before setting up Office 365 you should have an account with Microsoft or can form a one. Then go to your account and search for Office 365, the page will show you the product and the detail. You will also see the 1-month free trial option and the subscription option.
Select your product and choose the mode of payment. You will get the product now the process of installation will start.
2- The sign-in page will open.
3- Sign in to your account and remember you have to sign in to your office 365 with your paid account.
4- After you select your account, enter the MS office account credential and sign in.
5- The Microsoft team will recognize you as a premium customer and will take you to the installation page.
6- Now click the install office button and start installing.
7- Change the setting according to your system preference.