You can earn them with good content through getting upvotes. Or/And you can buy them on steem-engine.com. As soon as you have Palcoins staked you can also earn them with voting other content.

Here are two good posts that explain PAL:

• https://www.palnet.io/palnet/@juliakponsford/palnet-the-dazed-and-confused-user-guide
• https://www.palnet.io/minnowsupport/@minnowsupport/how-to-palnet-io-and-palcoin-with-keychain-and-steem-engine-com