To create a free Steam account, navigate to Steampowered.com. Click Login to be taken to a Web page where you can either log in or create a new account.
Click the Join Steam button on the login page at Steampowered.com to access an online registration form. Input a Steam account name, password and valid email address. Steam account names can be made up of uppercase and lowercase strings, letters, numbers, symbols and spaces. There are no restrictions on the length of a Steam account name and no banned words. Account names can be customized further once you have full access to your profile.
Once you have completed your personal details, answer the CAPTCHA task, and click the check box next to "I agree and am 13 years or older" under the agreement, then click Create Account on the bottom right.
Enter a valid email address to complete the last registration step. This address is used to confirm purchases and manage access to your account across multiple devices. During the registration process, Steam uses the email address that you supply to confirm your account creation. A link is sent to you via email; click it to verify your new Steam account.