You can add a card to discards by using an action and paying (removing 2-3 from the game to get 1 large value) with element cards from you hand or by destroying a curse (which takes 4+ element cards) which rewards you with a single element card.
You'll be spending a LOT of element cards to do things plus place in support. Your deck won't get very big at all.
I don't believe any of this is correct. The only time you remove cards from the game is when something specifically destroys them. Otherwise you are discarding cards when you spend them. I made the mistake of getting rid of my spells that let me destroy cards so in later rounds my deck was clogged with 1 value cards when I needed some bigger ones.