Start with the basics. Pull the sparkplug and ground it and see if you have spark when trying to crank. If that is good then it's probably fuel system. Is the petcock open giving fuel to the carburetor? After this things get to be more for the mechanically inclined
Carburetor is a common problem. If it has had gas with ethanol used, if it has been stored without draining and proper products, then find s small engine repair shop.