If you want to install VSTa, you should first read the VSTa install tutorial .
The VSTa roadmap describes where different stuff can be found in VSTa, and also helps to get VSTa going.
The VSTa release notes lists the new features in each version of VSTa.
Some papers concerning different parts of VSTa has been written:
Here's one very outdated document. But it might still be interesting
If you want to develop VSTa, these documents might be useful to read.
The VSTa manual pages written so far