The C1 value is a capacitor value and the L1 value is an inductor value. You will need one of each for each tweeter. At the bottom of that page it shows you the schematic of how to wire each into the system. basically the inductor will be wired in parallel (one lead to each terminal/input of the tweet) and the cap will be wired in series (inline with the + terminal of the tweet). Hope that helps.
Personally, I wouldn't do it quite this way...either go with the passives that came with the setup and use the amp for everything, or wait to get a four channel amp and run active.