The pyridinium ion is the protonated form of pyridine. The structure of pyridine can be seen here:
http://www.chemspider.com/Chemical-Structure.1020.html. The pyridinium ion has the formula C5H5NH+, and is just the protonated compound. Since methylamine is CH3NH2, the neutralization reaction will be:
CH3NH3 + C5H5NH+ --> CH3NH3+ + C5H5N
You should probably draw out the structure of the pyridinium ion and of pyridine, but that might not be necessary.