First welcome the fun of muzzleloading. And I agree with both above post. You can buy some 50 cal/.45 bullet sabots or 50 cal/.44 bullet sabots and the appropriate bullets. As Cayugad mentioned XTPs are good and my personal choice. I like the 300 grainers.
As for the cleaning aspect. Definately get and use a black powder or black powder substitute cleaner. There are several out on the market. Probably the easiest to get is Thompson Center's T-17. Its a great cleaner. I normally strip the gun down, swab the bore and when clean, run an alcohol patch down to dry it. Then give it a nice coat of quality gun oil. (be sure to remember to swab that oil out with a dry patch before shooting). Then clean the other parts paying close attention to the ones that get powder residue on. You want to clean that off and oil them so they don't corrode on you. But be careful again with the oil. Gun oil will contaminate a #11 cap really quickly.
One more thing. Be careful shooting your muzzleloader. A practice I've always done is after I shoot a load off, I blow down the muzzle. This serves 2 purposes: 1 It verifies the flash hole is clear (visible smoke coming out) and 2. It helps to extinguish any powder embers in the bore. (It wouldn't be any fun dumping another load of powder down the bore and havingit flare up in your face) So #3: watch where your muzzle is pointing during loading.