Hi! In the "Tiles (CHR)" module there is a button for you to "Swap CHRs". An alternative would be to export the CHR pages and import them manually to the correct banks.
Sometimes though what you want to do could be to keep the CHR pages where they are but assign them differently to the nametables and sprites. In that case you would use the "BG CHR: #" button in the "Background (NAM)" module and the "SPR CHR: #" button in the "Sprites" module.