At this point a SHARCNET account is no longer required to access Compute Canada systems (including those managed by SHARCNET). These can be accessed using your Compute Canada username and password. You can apply for it here.
If you are one of the few people who would find a SHARCNET account useful (to access one of the very few remaining legacy systems, for example), please email firstname.lastname@example.org to request one. In the email, please provide a specific reason for why you would need it.
Our previous (now outdated) information on obtaining a SHARCNET account is archived here.