To create the contracts for MST token and MST crowdsale, you need to create MSTToken.sol and MSTCrowdsale.sol files under the contracts folder. According to the contract feature, you can have any appropriate name for your contracts.
You can use Remix IDE or any other file editor to write the Solidity files. However, some plugins are supported for certain editors, for example, IntelliJ IDEA plugin, Visual Studio Plugin, and Package for Sublime Text. Now, let's create the MSTToken.sol contract.