Purchases you made in Viveport will be associated with your HTC Account. If you've already downloaded the content prior to the re-installation, your content will be seen in My Content tab.
However, if you're using a new computer, you do need to re-download the content.
- From your computer, open the Vive app.
- Sign in with the same HTC Account you used for the purchase.
- Under the Downloads tab in the Library, find the VR content and click Download.