Battery cable installation question

[underliner6]

Total noob confusion.

I just bought a new battery for my truck. Sears Die hard AGM with side posts. My old battery had top posts so i had to buy new battery cables to accommodate the side posts. I hooked up the positive cable to the alternator and hooked the negative cable to the side of the engine block just like the old ones were. Then i connected the positive cable to the battery with no problems. But when i make contact with the black ground cable to the negative side of the battery it sparks like hell not allowing me to hook up the negative side.

Im not really interested in electrocuting myself or blowing up the battery in my face...

What am i doing wrong?

Thanks for your guy's patience and information in advance!

Jim