All payware you are entitled to use as a Gold member will show in Content Store. (bottom button on startup splash screen) - If your bottom button says "Purchase Content" instead of "Content Store" and you are Gold, then something is not right. Mention that in a reply.
When You click Content Store payware should have "Install" button on right side. If there is a price showing instead of install then try this: Log into your account on Trainz website, Click on My memberships (on left side of screen), click Content Vault, then click the orange Select button. Then go back to your Content Store and the item should appear with the Install button.
As a side, I still have items in my content vault that I have never selected and they only show a price in Content Store. Yet new beta routes and such automatically just show up with "install" button active.
This procedure is currently under change and so it's a bit different for Gold and Platinum members and it's a bit confusing as it's in a transition mode between versions. The Content Store is brand new.
