I get the sha256d part but how can I broadcast my hash to other the nodes?
Well, you'll probably have to run at least some kind of daemon... You'll need to connect to other node(s) and then send them your block. More info can be found here:
https://en.bitcoin.it/wiki/NetworkIf you'd run the reference client node, you could use the submitblock json-rpc call... it seems chainquery does not support this call:
https://chainquery.com/bitcoin-cli/submitblockI don't know any online tool or service that offers this feature. If you read all protocols, you'll probably be able to build a much lighter client, one that only connects to other nodes and relays your block, but i don't think this is something you can do using binary's available on your OS, nor do i think there are sites out there that'll help you with this either.
Now, just to be 100% sure, this is all for learning purposes, right? Cause, there's no way you can actually pull all of this off IRL... You have allmost no chance of solving a block using a latest gen ASIC, let alone an older ASIC, let alone a FPGA, let alone a GPU, let alone a CPU... So your odds of solving a block, even if you'd find a good nonce by pure miracle, are 0 (since there's no way on earth you'll be fast enough generating a block, a block header, a sha256d hash and broadcast it in the ~10 min window)