How do I add regular lands? Where do I save downloaded Decks

I just downloaded Forge have a couple of newb questions.
I can't seem to figure out how to add regular land cards to a custom deck.
Am i missing something obvious?
Also where do I save downloaded decks? I download the pack that has 470+ decks.
I can't seem to figure out how to add regular land cards to a custom deck.
Am i missing something obvious?
Also where do I save downloaded decks? I download the pack that has 470+ decks.