The hose bib should just fit into the hole you've made. Hold it as perpendicular to the bucket surface as you can and screw it into the bucket. You may be tempted to make the hole larger, but it should thread itself onto the bucket. For added leak-proofing place a bead of silicone around the hose bib on the outside of the bucket before you screw it in all the way. Then screw in the spout the rest of the way, turning it until the spout is pointed down.
At this point, the spout should be firmly in place, but since this is going to be moved around some extra reinforcement is advised. On the inside of the bucket place the conduit locknut onto the hose bib and tighten.