I am very new (I was using photoshop) and I cannot figure out how to reduce the size of the tif files. Is there a setting for this?
Are you trying to downscale (reduce the pixel count)?
If so, open the tiff in Rawtherapee, go to the transform tab, and use the resize tool, to set a lower output resolution.
Also, export a jpeg, if you further want a file size reduction (does not change the pixel count, but does lose quality if the quality is set low).