So I have a project I'm trying to do. I want to have 2 displays (oled 32 screen) in the project, but the codes I'm running for them are taking up alot of storage space/temp memory. I'm thinking I want to hook up 2 nano boards to a mega board and have the nanos control the displays while the mega receives inputs from sensors, and push buttons. I know how to do the display coding, but I'm utterly lost on how to make the board communicate. Especially 2 boards serial communicateing with the mega. I understand the wiring, but would greatly appreciate advice on the code.
but I'm utterly lost on how to make the board communicate
That is why it is normally a bad idea to use more than one Arduino in a project, it adds more compilation that it is worth.
While the OLED displays take a lot of memory you have that available on a Mega so why use the two extra processors? It can drive two displays.
If you want text only you can get libraries that only use a few bytes instead of the large amount needed for graphics work.
What sort of display do you have? That is I2C or SPI?
If you must use more than one Arduino, and in this case I do not recommend it, you can communicate using I2C, there are examples of doing this in the IDE.