Caulk the floor
Set toilet up and lay out tape of the exact sizing of the bottom of your toilet. Remove the toilet and turn it on its side.
Cut the Caulk tube tip square and drag the caulk gun towards you as you lay a thick bead of caulk along the inside edge of the tape.
Toilers should be caulked to the floor to prevent movement, which can break the wax seal used to prevent overflows. This is also a prevention of leaks and puddling, which can in turn rot the floor.
DO NOT set toilet and then caulk. This will not work as well as if you did it before toilet placement. It will leave a permanent line.
For a professional toilet installation call D&D Plumbing Heating and Air!