Clear it in 3 steps
Start the environment
Investigate the target
Submit the flag

A legacy server was administered over Telnet in clear text. Download the packet capture (traffic.pcap), follow the Telnet session, and extract the login password. The password is the flag.
Telnet is clear text on TCP port 23; filter with tcp.port == 23
Right-click a packet and choose Follow -> TCP Stream to read the whole session
tshark -r traffic.pcap -q -z follow,tcp,ascii,0 dumps the stream contents