I have a toilet that sits an a concrete floor. When the builders refurbished, they put down laminate, and glued the toilet to this. So there are no bolts in the concrete.

How can I secure the toilet to the floor?

Can I simply drill down and attach with screws?

The toilet should be secured to the floor flange with toilet hold down bolts. The floor flange is secure to the floor with screws.

At this point we don't know if the flooring installer just failed to reinstall the hold down bolts or if they loosen the floor flange from the concrete to run the laminate under the flange. We also don't know what kind of flange you have. It could be PVC, glued to PVC pipe or it could cast iron, leaded to cast iron pipe.

You will have to pull the toilet to see. Most likely the laminate was cut around the flange and you will need only to install the hold down bolts in the flange and reset the toilet. The flange should be flush with the top of the laminate or protrude about 1/2" above. If it is not flush install an extension ring.

If the flange is PVC and not secured to the floor post back.

Always use a new wax ring when resetting the toilet.