Here is some information found:
The child bike seat can be easily attached and removed from the bicycle. With an extra support, you can easily move the child seat from one bike to another. With the Siesta child seat, cycling with children is safe. The Siesta child seat is equipped with a lockable bracket that allows it to be securely fastened to the bicycle.

It can be attached directly to your bike and you can buy an adapter to attach it to several bikes.