There are anchor cables that usually are implanted in the ground in order to stabilize the batting cage and the poles. themselves, are usually inserted into the ground. Many people have figured out workarounds for both indoor and use on concrete pads.
One of the possible workarounds is embedding steel loops into the concrete that the cables can be anchored to and drilling precise holes that the poles slide into. Another method that many have used is filling buckets of sand and embedding the anchors and poles into those buckets of sand. For a better idea of what may be involved, please view the Owners manual/assembly instructions for the batting cage.