Can someone educate me on what to look for when getting a fish finder. Does it come with everything I need or do I need to buy other things. It's going on a kayak so do I need a portable fish finder? Any kayakers or boat person help a fellow fisherman out.

If, by everything you need, is a head unit, a mount, a transducer, and wiring, then yes it does, although some units can be purchased without transducers.. I'm not familiar with a kayak set up which may require some different mounts. You will want to install an inline fuse which is not included. You can pick up a fuse holder and a package of 3 amp fuses at the auto parts store. If you meant what features you need, you'll have to figure out what is important to your style of fishing. There are tons of options available. I'm sure a kayak guy will chime in shortly.

Will I know how and where to install an inline fuse?

At or near the battery. Here's a pic of one on amazon. All you would have to do is cut the red wire in the middle. Strip both ends. Attach one end to the graph +(red) wire using a butt connector and some shrink tubing. Attach a ring connector large enough to fit around the battery terminal to the other end and connect to battery. Install a 3 amp glass fuse. Everything you need should be available at an auto parts store. http://www.amazon.com/dp/B000A8E0KI/ref=asc_df_B000A8E0KI2548509?smid=ATVPDKIKX0DER&tag=pg-1257-86-20&linkCode=asn&creative=395097&creativeASIN=B000A8E0KI

Dick's sells kayak units in a kit with a small battery.