Welcome to the Forum!
Have someone help you with this, First, start your bike without the seat on. Turn on ALL your accessories, keep the idle of the bike at around 2000 rpms, and check the voltage across your battery. Then turn any accessories you can OFF and test the voltage again. Any voltmeter should work, just make sure you have it to test direct current DC, not alternating current AC!
To "charge" the battery your alt will need to output 13.5 volts or more. Actually you really need it to read 14 or over.
If you read less than 13.5 volts, you have somekind of alternator fault like a broken winding or bad wire maybe?
Good Luck and please UPDATE us on the outcome!