To filter Newsletters from StackExchange you'd enter the following into the filter boxes:
The from field will look at the email address or the senders name (in this case both: (email@example.com)
and the Subject field will look for any matching words in the subject line (eg: Web Applications Weekly Newsletter - Tuesday, June 5. 2012).
A filter setup like the above screenshot will label only the StackExchange newsletters, handy for if you want to make the newsletters skip the inbox, but want all other stack communication to stay in the inbox.