Signing up will give you access to the free version of the Structurizr cloud service, with the basic feature set as described on the products page. You will need to verify your e-mail address to use your account, so please check for typos.
Signing up on behalf of an organisation? Consider using a shared/group e-mail address to ensure continuity of access when individuals leave your organisation, or are otherwise unavailable. See Help - Corporate accounts for more details.