Sending transaction from light wallet to RPC (push_tx)

Hello! I’m trying to send signed transaction to a trusted Node on another computer through RPC endpoint /push_tx. I have my wallet mnemonics with me but I can’t find out how to create aggregated signature nor puzzle and solution. Does anyone know how to handle creation of signed transaction and sending it to some address? I’d be very grateful for any answers.
I was following the but I am stuck at getting the serialized puzzle and solution. How do I get those?