It's in the top-right corner of the Gmail inbox. A drop-down menu full of icons will appear. This option is at the bottom of the drop-down menu. Doing so opens a second page of icons. It's a blue-and-white person-shaped icon. This will open your Gmail Contacts page. Depending on whether or not you've used Gmail before, you may see a few contacts here. Contacts may range from only names to full profiles including names, addresses, phone numbers, and email addresses. It's in the bottom-right corner of the window. Doing so brings up a pop-up window. In the "First name" and "Last name" text boxes at the top of the pop-up window, enter your contact's first and last names, respectively. Type the contact's email address into the "Email" text box. You can add additional information, such as the contact's phone number or a contact picture, but doing so is optional. It's in the bottom-right corner of the window. Doing so saves your contact and adds them to your account's contact list. If you want to remove a contact, do the following:  Hover over the contact's name, then click the checkbox that appears on the left side of their name. Click ⋮ in the upper-right side of the page. Click Delete in the drop-down menu. Click DELETE when prompted.

Summary:
Click the "Apps"  icon. Click More. Click Contacts. Review your contacts. Click the "Add"  icon. Enter the contact's first and last name. Enter the contact's email address. Click SAVE. Delete a contact.