Select a campaign and click on 'Add publication'.

Create a publication name, tag (optional) and choose publication type: 'Print Magazine' and choose the workflow. Then click on 'Create'.

The print publication has now been added to your campaign.

Now click on the publication you have added. To fill your print magazine with pages, first click on 'Single and/or Spread'.

Then choose the template for your page(s). Then click on 'Add'.

In the step 'Add Pages' you always can enlarge your print publication by adding pages and/or spreads until you are done.

After adding the page(s) you can start assigning the briefing items to the page(s).
See: https://help.relayter.com/en/articles/2304661-assign-briefing-items-to-a-print-magazine-or-leaflet