More info needed. What is the canopy made of? Is it one of the kits with the canopy that fits around a frame? What is the structural support for it like? Are there tent like tie downs? Picture possible?
If it is a kit that fits around the frame and you have not tied it down, add some deck cleats and hope tying it to them keeps it from blowing off. Those things can be like runaway sails. If it did not come with them, you may have to add some grommets so you do not rip the fabric to pieces. A grommet kit is not expensive.