General Thread for practicing questions formatting!

[haojiayang]

function fund() public onlyOwner {
        require(msg.value.getConversionRate() > MINIMUM_USD, "Didn't send enough!");
        funders.push(msg.sender);
        addressToAmountFunded[msg.sender] += msg.value;
    }

On this function, I'm runing into an error:

TypeError: "msg.value" and "callvalue()" can only be used in payable public functions. Make the function "payable" or use an internal function to avoid this error.

Can someone tell me what's going on?