In order to open a Wealthsimple Crypto account, you'll need to have a Wealthsimple Trade profile. You can follow the steps outlined in this article to set up a Wealthsimple Trade profile and download the mobile app (if you wish, Trade is now accessible via desktop also).
Once you have a Trade profile established, open the menu and select "Manage accounts". Then, select "Open a Crypto account". Follow the prompts, and once done you'll be able to deposit funds to your new Crypto account.