There's many different guides for setting up Evolution for Gmail, but I haven't found a perfect one. So here goes yet another one.

Receiving mail with Evolution:

• Server type: IMAP+

• Server: imap.gmail.com

• Port: 993

• Username: first.last@gmail.com

• Use secure connection: SSL encryption

• Authentication type: Password

Sending mail:

• Server type: SMTP

• Server: smtp.gmail.com

• Port: 587

• Server requires authentication: yes

• Use secure connection: SSL encryption

• Authentication type: Login

• User Name: first.last@gmail.com