If you are using an MM, you need to make the changes on the MM. For example, if I have an MC named 7005-6b, I can navigate to the device node for that MC, go into "conf t" mode, set the logging level, then save the changes, all shown below
(MM1) [mynode] #cd 7005-6b
(MM1) [00:0b:86:b8:62:xx] #configure t
Enter Configuration commands, one per line. End with CNTL/Z
(MM1) [00:0b:86:b8:62:xx] (config) #logging network level debug
(MM1) ^[00:0b:86:b8:62:xx] (config) #write mem
Saving Configuration...
Configuration Saved.
Then to look at the logs, you will need to console or SSH to the MC itself. The following shows the log levels before and after the previous commands were run. When you are done, you need to go back to the MM, and issue the commands again, returning the logging level to where you started.
(7005-6B) #show logging level
LOGGING LEVELS
--------------
Facility Level
-------- -----
arm warnings
network warnings
security warnings
system warnings
user warnings
wireless warnings
(7005-6B) #show logging level
LOGGING LEVELS
--------------
Facility Level
-------- -----
arm warnings
network debugging
security warnings
system warnings
user warnings
wireless warnings
I hope this helps,