Not directly. If you do, the signal from your guitar won’t be loud enough to be heard and it won’t sound its best because the Ceres inputs require a much “hotter” signal than most guitars produce. To use a guitar with the Ceres speaker, you will need to plug your guitar into a DI (Direct Injection, or “direct”) box, then plug the output of the DI box into the Ceres TRS input.
PreSonus makes the TubePre V2, a high-quality preamp that also serves as a DI box. More information can be found at www.presonus.com/products/TubePre-V2.