Summarize:

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.
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.