I need to cover an area approx 20 feet by 8 feet. How do you recommend installing these, so they all stay together? Is there some sort of tape to achieve this?

You don't have to glue or tape our mats together for them to stay in place, but if you wanted you can use some double-sided tape along the seams, or you could do a full spread glue install. The mats themselves are very heavy and will be tough to move when performing most exercises.