Provide yourself a forced situation
What it meant is simply put yourself in situations where you are forced to actually use the language. Ironically, that is how we as humans learn the fastest. You can do this by watching Spanish movies, reading Spanish language newspapers, travel to Spanish speaking countries or even befriending a Spanish friend. If you want to pick up common idioms fast, pronouncing slangs and accents just like native speakers, your best bet is to have frequent interaction with Spanish native speakers. That way, you sound like a native a lot quicker.
If you cannot travel to Spanish speaking countries or you want to go with a basic level of Spanish, a good online course could be your solution.