The heart has a hole vertically top to bottom. To see how you make it into a pendant, take a look at our Design Center in the Pendants section.
Here's a similar one. To use this 35mm heart, you'll need a 3 inch headpin to give yourself plenty of space for the wire wrapping.
http://www.venetianbeadshop.com/Venetian-Red-Heart-Pendant-Necklace_c_1356.html