yea click the fx button you should see a folder, i.e. the 'open' button. Click that go through explorer and find your vst. I set up a folder in program files called vstplugins and i just copy all my plugins there and it automatically generates in acid since I selected that folder

Does acid come with plugins or do you have to download them seperatly??

depends. With the crack that most people use, it should come with some standard plugins that honestly are quite good. The compression/limiter VSTs are the main ones you'll want to search for (and specialty VSTs like a backstop)