You buy empty bottles from the website store. You select the empty bottle to put in your 'level inventory' on the inventory section. You use the mouse wheel or the inventory buttons to select the empty bottle and find a 'water cooler' to fill the bottle before placing it on the desk in the same level, otherwise it doesn't count.
The green bottle is where the filled lube bottle is placed, not where you get it from.
This has been asked before so many times that I'm assuming this is what you're asking even though you haven't said much beyond 'It doesn't work'.