click on the 'Windows' button (formerly the 'Start' button) and type Windows Memory in the search box. The Windows Memory Diagnostic item will appear at the top. Click it and at the restart prompt choose restart. The windows memory diagnostic tool will test your RAM. You can change the memory test parameters while it is running. The hot keys are at the bottom of the screen.
The standard test is 2 passes. I imagine the standard test will run within 5-10 minutes on your PC. If you change any of the parameters, it could run longer depending which you choose.