General questions about practicing question formatting

[abedgithup]

function fund() public payable{

 // require(msg.value.getConversionRate()>= MiniMUM_USD ,'did not send enough');
   funders.push(msg.sender);
   addressToAmountFunded[msg.sender] += msg.value;
 }

I am running to an error:

from solidity:
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 help?