When you turn it on with the plug inserted, it automatically tries to repair the calibration constants. You don't have to do anything.
Since you replaced the battery, you've probably lost everything because the constants are only held in RAM. No battery = no data.
Your only option at this point is to work your way through the calibration procedure in the manual.
AFAIK, there's no way to backup the constants before a battery swap. That's an unfortunate gap in the meter's design.
Actually, the battery backup is a sloppy design to begin with. Since you've already lost the data, now would be a good time to update the circuit. The battery voltage is only 2V4 and there's a diode in series between the battery and the RAM chip. That puts the RAM voltage too close to the minimum value even when the battery is fully charged. Revising that circuit is somewhere on my list of future projects. My plan is to increase the battery voltage to 3V6 and adjust the charging circuit to match.
Ed