Hi Keith

First step is to see if the kernel has picked up any network devices.
Run dmesg(1) and look for a line 'Ethernet Address' - here's my snippet:

...
fxp0 at pci0 dev 11 function 0: Intel i82557 Ethernet, rev 8
fxp0: interrupting at irq 5
fxp0: Ethernet address 00:d0:b7:80:d0:54, 10/100 Mb/s
...

The device name is at the beginning of the line, so in my case I have a fxp
device. Your case will depend on the device type, there are several.

Second step is to get the interface up and running, for that you use
ifconfig(1). In my case,  on the command line:

ifconfig fxp0 inet 192.168.1.1 netmask 0xffffff00

If you do an ifconfig -a, you should see that the interface is up in the flags
section. You should now be able to ping(1) hosts on the local wire. If you have
a router, remember to add a default route.

To make the interface permanent, create a file /etc/ifconfig.fxp0 and put the
arguments into the file. Here is my file:

% cat /etc/ifconfig.fxp0
inet 192.168.1.10 netmask 0xffffff00

As to pkg_add, it should be in /usr/sbin. Are you running pkg_add as root?
/usr/sbin should be in the root path.

Hope this helps - welcome to NetBSD!
--et