Connect SDRAM to STM32
As far as I know, you have to choose variant with FMC module (Flexible Memory Controller) with SDRAM support - that means you have to use 144pin version STM32F730Z8. The 100pin version does have FMC but doesn't support SDRAM.
After resolving this issue, it should be about configuring FMC module for using SDRAM (in STM32CubeMX for example) and the RAM will be available at some memory location according to the MCUs memory layout.