Admin Console --> System --> Settings --> Home Page
Thanks for posting this question on how to set the default landing page to "Home". You'll want to enable the Home Page first as Xavier has pointed out, but will also need to set the default landing page via System Property. I'm not sure which version of Jive you're on, but I'll link to the Jive 8 documentation here which covers the topic:
With special attention to:
If you want to choose a different community page as the default for all users, you can use the skin.default.landingpage system property to set it to any of the Home pages. Check the URL of the target page for the correct value. For example, to set the default page to Activity, set the value to /activity.
I hope this helps. Let me know if you had any other questions on this.