to create network you need to create first block in the network which is called Genesis block

to create it use this command:

geth --datadir folderToStore init genesis.json

genesis.json is the file which contains config for the Genesis block use puppeth tool for creating it

to launch blockchain use this:

geth --http --http.api web3,eth,debug,personal,net,miner --datadir blockchain

after that you can create account like that

// create and unlock account
personal.newAccount('password')
//address _output

// while testing you might need to ignore signing transactions for simplisity
personal.unlockAccount("_output", "password", time exm: 15000)