With the Nvidia Control Panel -> Desktop -> Add “Run with grafics processor” to context menu you can add the selection of the grafic card to the program icons.
Then you can right click on the sketchup icon and select the nvidia card to run.
There is also the option to setup sketchup to run with nvida-card in the Program Settings in Nvida control panel. Select or add sketchup.exe and then you can set the default grafic card.
When you control panel does not show these options, then its a good time to upgrade your nvidia driver…