To create a new journey from a Primary Campaign you previously made and saved, locate the campaign and create a new journey for it. (It must have an approved status.)

Create a New Journey from an Existing Primary Campaign

Select Campaigns > Manage.

Locate your campaign easily by clicking the Approved tab.

In the Status column for the campaign, click Approved.

In the pop-up, click Ready to Schedule.

Select Create Campaign Journey.

Build Campaign Journey

Proceed to step 4: build a campaign journey.