The kanji can mean enchanting, and that's what this adjective means too: enchanting! You could even call it bewitching.

妖しい is for mysterious, eerie, or beautiful and otherworldly stuff that bewitches you somehow. Try not to get it mixed up with 怪しい (suspicious), which has the same reading!

This word uses a kun'yomi reading you haven't seen yet, so here's a mnemonic:

Who has an enchanting atmosphere about them? Aya (あや). As in our artist Aya. Not only is Aya enchanting, so is her amazing artwork.

Since this word also shares a reading with 怪しい (suspicious), which you learned a while ago, you could remember it that way too. Just don't get them mixed up!