Copy paste following template into your Squidman template
# ----------------------------------------------------------------------
# WARNING - do not edit this template unless you know what you are doing
# ----------------------------------------------------------------------
# the parent cache
cache_peer %PARENTPROXY% parent %PARENTPORT% 7 no-query no-digest no-netdb-exchange default
# disk and memory cache settings
cache_dir ufs %CACHEDIR% %CACHESIZE% 16 256
maximum_object_size %MAXOBJECTSIZE%
# store coredumps in the first cache dir
coredump_dir %CACHEDIR%
# the hostname squid displays in error messages
visible_hostname %VISIBLEHOSTNAME%
# log & process ID file details
cache_access_log stdio:%ACCESSLOG%
cache_store_log stdio:%STORELOG%
cache_log %CACHELOG%
pid_filename %PIDFILE%
# Squid listening port
http_port %PORT%
# Access Control lists
acl SSL_ports port 443
acl Safe_ports port 80 # http
acl Safe_ports port 21 # ftp
acl Safe_ports port 443 # https
acl Safe_ports port 70 # gopher
acl Safe_ports port 210 # wais
acl Safe_ports port 1025-65535 # unregistered ports
acl Safe_ports port 280 # http-mgmt
acl Safe_ports port 488 # gss-http
acl Safe_ports port 591 # filemaker
acl Safe_ports port 777 # multiling http
acl CONNECT method CONNECT
%ALLOWEDHOSTS%
%DIRECTHOSTS%
# Only allow cachemgr access from localhost
http_access allow localhost manager
http_access deny manager
# Deny requests to certain unsafe ports
http_access deny !Safe_ports
# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports
# protect web apps running on the proxy host from external users
# http_access deny to_localhost
# rules for client access go here
http_access allow localhost
%HTTPACCESSALLOWED%
# after allowed hosts, deny all other access to this proxy
# don't list any other access settings below this point
http_access deny all
# specify which hosts have direct access (bypassing the parent proxy)
%ALWAYSDIRECT%
always_direct deny all
# hierarchy stop list (squid-recommended)
hierarchy_stoplist cgi-bin ?
# refresh patterns (squid-recommended)
refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440
refresh_pattern -i (/cgi-bin/|\?) 0 0% 0
refresh_pattern . 0 20% 4320
# hosts file
hosts_file /private/etc/hosts
In Client tab add following wild card entry
192.168.1.0/24
This entry may depend upon your network settings;