Realize it or not, you are already doing it. Integrated graphics chips don't really have their own pool of memory to use, so instead they use the system memory. A portion of this is segmented for use just by the iGPU.
For example, if you have 8 GB of system memory, but you check with a monitor and it says you only have something like 7.5 GB for example, it is because the 0.5 GB is allocated for the integrated graphics.
Is this a laptop or desktop system you are using? If it is a laptop, unfortunately you may not be able to change the amount of RAM dedicated to it. Although, in my laptop when I increased the RAM I had, it likewise allocated more to the integrated graphics. I don't have any options in my laptop though to increase this...