Select 'Configuration Manager'
Active solution configuration > Release
Active solution platform > Select New. Then select x64 and it will create the new configuration (if it doesn't exist then 64bit compilers are not installed)
To build the x64 executable just select x64 from the projects drop down on the toolbar. Note that it will be created in a new folder called x64, not he default 'Release' folder.
Normally this is all you need to do but you need to consider tweaking a few pre-processor defines, maybe for the intellisense.
As for libraries, for platform ones (supplied as part of VS/PSDK) you dont need to change anything. For your libraries you are adding that have alterative versions change the Additional Library Directories in the project properties to point to the 64bit directory.