Most kanji have multiple readings. It’s better if you learn each reading through new vocabulary. If you go to the dictionary and select the “Kanji” section, you can search for a specific kanji and see each reading along with the words it can be found in.
This is the rule of thumb but whenever kanji are sticked together like that you'll read them in what's called their onyomi reading, which is basically the reading derived from China. I recommend giving a look at the renshuu lesson going over Kanji
