All APRS commands are single keys.
The commands are usually spelled out but only the first letter of each command word is needed. Verify reception by observing the DCD lamp whenever data is heard. Verify proper decoding by observing the L and P lists for collection of packets from other stations. Hit the OPS-PING command to force your system to transmit. Within a second or so, and after the channel is clear, your transmitter should key up for about a second.