Hi
I'm not sure what you are trying to do, but as you know, your computer has an Intel HD 520 graphics card with 128MB of VRAM. The RAM your graphics card has is the RAM it has, you can't make it have more RAM.
Unfortunately, you don't have another graphics card in that computer, which means it doesn't meet the minimum requirements of the game. 
Graphics Card: ATI Radeon HD 2600 or better*, NVIDIA 7800 or better*, Intel HD Graphics or better*
*Minimum of 256MB of on-board RAM and Shader 3.0 or better support.
As you were having this issue in the trial of the game, my recommendation at this point is to not purchase the game unless you have another computer that meets the requirements in which you could play.
I'm sorry I don't have better news for you. Have you considered taking a look to other SimCity games like SimCity 4 or SimCity BuildIt?
-Mai
