Help in Hidden Markov Modeling

Hi all...
I have a Time series counts(Observed Number of Infectants each Month).. I want to model it using Poisson HMM.. I am using Lindsey'd Repeated Library..
But I am not clear with the arguments like "mu", "pmu".. etc.. How can I decide on the number of states... Is there anybody to help me...
thanking You All,
Regards From,