You need to specify your AFL output directory with `--fuzzer-directory`, and your peers with `--peers`.
Some other options exist to let you fine-tune your *afl-transmit* experience, have a look at them via `--help`.
On default, *afl-transmit* opens port 1337/TCP to wait for incoming connections. If you are not on a private net, make sure to protect this port with a firewall, or anyone on the internet may send you files (although this might become interesting).