We normally take 25% advance payment. Then we start working on requirement, development. Once we complete development then we will provide you testing on our server. You can test and ask us for any modification required. If any new changes are there then we will provide you new estimation. If any error or changes are there from existing requirement then we will solve asap and you can confirm. Once all running fine, then you can make remaining payment. And we will provide you module by email. You simply have to install module and it will work. We can provide you steps to install module if required.