Telus does not support forwarding SMS at the network level. There is no setting or website you can visit to turn on SMS forwarding. The ancient website they used to use that allowed you to log in and view your SMS history on the web was disabled many years ago (August 10, 2008) without a replacement (old web interface had major security issues is what I heard)
The only option is to find third party apps that can run in the background of your phone to forward messages. It would require your phone to be turned on and connected for the forwarding to work so if you wanted this for travel purposes you would have to leave your sim card running in a device while you were away.
Telus should offer an SMS forwarding solution but after 8+ years since the inbox feature was killed it seems like that's never going to happen. Suspect they want to prevent people from considering a cheap local SIM option when travelling so they can get you to pay their lucrative roaming rates.