To my knowledge, if the person you want to add has Telus services (e.g. Cellphone), you can add them through the 'My Account' portal. If not, you would need to contact Telus directly to have their name jointly added to the account, and identifying credentials created for them. You would then have to set up new, or share, your login credentials. Note that sharing a login is becoming more difficult as two-factor authentication becomes more commonplace.
NFtoBC If you find a post useful, please give the author a "Like"
You have to contact Telus. The telus.com linking account tat @NFtoBC is talking about is strictly for telus.com/app access. It doesn't give them access for calling in/going to store to make changes. You can call in/chat in and add them as an authorized name.