Start by reading the instructions!
Raritan SeaEra owners manual
If you're replacing a Jabsco--or any--manual toilet, you'll need to fill mounting bolt holes and drill new ones...and btw, all toilets mount using lag bolts, so no nuts to remove. Just back out the bolts.
All electric toilets should be on their own dedicated circuit, shared by nothing else--not even cabin lights--that can pull power away from it. 'Cuz low voltage is not only the most common reason for sluggish discharge, but is also highly damaging to any electric motor. If your electrical skills max out at replacing a light bulb, you might want to pay certified marine electrician to do that much. The rest is just follow the instructions, asking questions if there's anything you don't understand BEFORE you do it wrong and have to do it over.