Just bought my first mud motor a 20 hp Honda beavertail and was wonder how to grease it and how often to grease it. Can anybody please give me some advice

Bevertail probably has a manual or something on their website. Factory recomendations are usually the best.

Should be a fitting on the shaft, grease that fitting till grease/water pushes out of the seal Infront of the prop, then your good. Also should be a fitting near the universal joint at the top of the shaft. Grease it to to keep the noise down.