To refresh you just turn it off and back on. Or are you talking "Reset"? Which is to clear it off and put it back to its original settings. Which would be doing a "Hard Reset"? If you are talking the latter, then the instructions below should help.
NOTE: Doing this will clear 'all' the data on your tablet, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the device.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the tablet...
1. Make sure that the tablet is actually powered off.
2. Remove your SD card, if there is one in the device.
3. Press the "Power" and the "Volume Up" buttons, together, until...