.tmux.conf file located in your user's home directory you can change or add keyboard shortcuts to your tmux sessions. If this file doesn't exist you can just create it. There are lots of sample
.tmux.conf files around the web and several good gists out there.
If all you want to do is make comma or dot cycle to previous or next window add the following to your config file:
unbind n # Unbind 'n' and 'p'
bind-key , next-window
bind-key . previous-window
As always you can see current key settings in your tux session with CTRL+b (or whatever your bind key is, this is the default) then ? for help. To exit this
less style help screen just hit q.