Editing SSIS packages?

I have a package(.dtsx) file under Projects in Integration Services Catalogs. I have a requirement to: 1. Edit a specific package(.dtsx) file and make changes to it. The project has more than one dtsx files. There is no .sln file or a package file after I click on Export under Projects. A .ispac file is created which I extract to a local folder and then open the dtsx file in Data Tools to edit it. 2. Once this is tested after the changes are made, save the package back under Projects in SQL Server 2012. 3. Finally deploy the package to the Production server. Can you help me with the steps required to complete steps 2 & 3 and any alternate way to do Step 1? Thanks.