There is a simple example in the forum: Help me write an erc20 token and a crowdsale contract
Crowdsales are in OpenZeppelin Contracts 2.x (they were removed in 3.x). The documentation is here: https://docs.openzeppelin.com/contracts/2.x/crowdsales
There is a simple example in the forum: Help me write an erc20 token and a crowdsale contract
Crowdsales are in OpenZeppelin Contracts 2.x (they were removed in 3.x). The documentation is here: https://docs.openzeppelin.com/contracts/2.x/crowdsales