At first, the HelpDesk application should be added to your Jira. Read how to find, add and manage the Server apps (Atlassian documentation).

If you don't have the support-related projects create them as usually in Jira. Use any available project template – no matter if you have Jira Core, Jira Software or both.

The app doesn't work out of the box – it must be configured before, not to mention the projects, issues and workflows configuring required for the support process tuning. However, there are several features that don't need to be set up:

The initial settings are roughly the same as they are located in the documentation:

Others should be set up – please check the rest of the documentationThe HelpDesk app settings are located at Jira Administration → HelpDesk and are accessible for a user with Jira Admin rights.