Have a hummingbird 798ci HD was wondering where the best place to go to get info on learning how to use and read. I have no trouble catching fish, but I always see people posting saying they marked Here or there or they marked Fish 18 inches down in ten feet of water. I see shad and have a hard time figuring out if there's big fish near them or if I,m looking at structure or shad. Never used electronics before buying this so just trying to learn. I usually long line troll but would love to find structure and jig over it, but every time I find what I think is structure with fish I never catch anything. Help!