Hi Lucas - Welcome to the Atlassian Community!
Jira Service Desk isn't really a separate thing per se. But it's a type of project that then has features associated it that type of project.
So, create a new Project and select Service Desk as a Template type when you are creating the project. See if this previous post helps you a little:
Hey there Cloud Community members! We’re excited to give you the first glimpse of the new home for business teams on Jira — Jira Work Management. Jira Work Management is the next generation of J...
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