There are many positions (ways, variants etc.) to play the C major (triad) mandolin chord.
In this article you can find the most common chord positions – displayed on the slideshow above, fingered for your convenience.
To help you understand how to play them, I have included step-by-step instructions, describing where to place each finger and what note this will produce. Finally, the article includes a chord chart with all possible chord positions for future reference, feel free to print it.