easy peasy lemon squaeezy, really!
 
put 'em wher the sun dont shine (directly) - direct sunshine creates too much heat in the terrarium and the plants can scortch or sook in warmer weather.
 
if you see loads of condensation then take the lid of for a day to let out some of the moisture 
 
otherwise, just let the plants do their thing and leave the cork in place
 
trim plants that get a little tall or unshapely