click on the bag and drag this small pane next to your large inventory - now you can drag&drop your crystals from one to the other.
http://www.kiya1.de/beyond/actgeneral/crystalbag0.pngAlchemy extract+plants give you the opportunity to create your own potions.
http://www.kiya1.de/beyond/actgeneral/alchemyplants0.jpgAlchemy combine allows to create white ones, by dragging
blue over red potions
red over yellow potions
blue over yellow potions
In order to create or combine you need to have the char with these skills either in single or leading mode. Plants have to be in the inventory of the char with the alchemy extract skill