In this exercise we're given a certificate, a private key file and a pcap with encrypted traffic. All we have to do is decrypt the traffic.
My copy of Wireshark was looking for an RSA key, so I had to run:
openssl rsa -in apache.key.hold -out apache.key
Now the key has been changed from PEM (supplied) to RSA (required) format.
Once I run that, I open the pcap in Wireshark, go to [Edit][Preferences][Protocols][SSL] and enter the info in the form <ip>,<port>,<protocol>,<key file> and press apply. In this case:
Bob's your uncle.