You need to have huge hashing power at first.
https://bitcointalksearch.org/topic/complete-guide-on-how-to-create-a-new-alt-coin-225690 this can help you.
https://bitcointalksearch.org/topic/complete-guide-on-how-to-create-a-new-alt-coin-225690 this can help you.
You don't need a huge hashing power, just remove the breakpoints and you will start at point zero. Just clone the Bitcoin Github source (like Litecoin, Dogecoin and so on did) and change the genesis block, change block time, total number of blocks and remove the checkpoints. If you have knowledge of c or c++ this is pretty easy. If you don't have any programming experience this might be too difficult.
The article mentioned is pretty complete.
