A back-of-camera LCD is not designed, and should not be used, for gauging exposure based on the brightness of the LCD. As noted by Dreamager in a comment, you can adjust the brightness of the LCD and that might better approximate how things look on your computer. Whether or not your computer is displaying an image accurately depends on if it's been calibrated or not.

To gauge exposure, use the histogram feature of the camera, which provides a graphical representation of the tones in the image from dark to light. There are lots of questions and answers about histograms here on this site, but here's a popular and detailed one:

How and why do you use an image histogram?

The histogram will allow you to identify if you're clipping highlights (very overexposed), blocking up the shadows (likely underexposed), or somewhere in between. That said, one could also argue that there's no "correct" exposure and that it's up to the photographer, but that's an entirely different discussion :)