How can I reduce size of my input

I have an FMRI dataset containing a matrix of (392)(392) (after applying correlation on the 1D file of FMRI). I have to apply Autoencoder on it. How can I reduce the size of my input? because my model will contain first line like this: self.fc1=nn.Linear(392392,__) this is huge to send it to Autoencoder.