Note: Their service provides free access numbers, but charges for receiving text messages.
Textr's Textr Go offers free American and Canadian phone numbers to users, allowing free reception of text messages/MMS, free phone calls, and the ability to send 100 text messages or 50 MMS for free each month, along with 100 minutes of free call time per month.
The specific steps are to visit https://textrapp.com/go/en/textr-go-download, download and install the Textr Go app, available for both Apple iOS and Android versions, from their respective app stores.
Registration is also very simple.