Need to add some code but do not know where

[Disasterpiece]

1) Easiest way would be to create a plugin with hook @ global start (or similar, not sure how it's exactly called) and insert the code there, so you could make sure that the inclusion is available throughout the whole script call.

2) This code won't work in template files, you can't use php code. A plugin which works with template-hooks seems to be the easiest way to realize this without modifying vb core files.