Summarize the following:
Go to https://www.gmail.com in your computer's web browser. This will open your Gmail inbox if you're logged in. If you aren't logged in, enter your email address and password when prompted. It's in the upper-right side of the page. A drop-down menu will appear. This option is at the bottom of the drop-down menu. It's a person-shaped silhouette on the second page of the drop-down menu. This will open a list of your contacts. You'll find this option in the lower-right side of the page. Clicking it prompts a pop-up window. Type their first name into the "First name" text box, then type their last name into the "Last name" text box. Click the "Email" text box, then type in your contact's email address. You can enter other information—such as your contact's company, job title, and/or phone number—but doing so is optional. It's in the bottom-right corner of the pop-up window. This will save your new contact and add them to your list of Gmail contacts.

Summary:
Open Gmail. Click the "Menu"  icon. Click More. Click Contacts. Click the "New"  icon. Enter your contact's first and last name. Enter the contact's email address. Click SAVE.