You don't need to use integrated graphics to install your new hardware.
Just turn off the power.
Remove the R7 240 card from the system by disconnecting all cables running to the graphics card, unlocking the slide lock at the PCIe slot, remove the screw holding the card to the back of the case.
Install is the reverse order.
Power up.
Once you are in Windows, or you can download it to a flash drive or other external media like an external hard drive, download the latest driver version from here:
http://www.nvidia.com/download/driverResults.aspx/129081/en-us
Install the Nvidia drivers, restart, done.
You don't need a different card or integrated graphics to do that. The card will work with basic functions as long as it is installed, your video cables are plugged into it and any necessary power cables are connected to it from the PSU, if that card uses any. Most 1050ti models do not need supplemental power but there are a few models that require it. If yours needs it, connect it. If not, ignore that step.
Once you are in Windows you can run the Nvidia driver package you previously downloaded, then restart afterwards and that should be the end of it.