ACS 723 Current Sensor
You start with the datasheet.
For each specific module, there is a table that gives you a &quot;Zero Current Output Voltage,&quot; and a &quot;Sensitivity.&quot;

Subtract the zero current voltage from your measured voltage then divide by the sensitivity to get current.
Assuming a Vcc of 5V and that you are are using the &quot;xLLCTR-5AB&quot; model (from the example table,) then your measured current (as shown in your example) would be around \$\frac{2.39V-2.5V} {400} = -0.275 amperes.\$

There are more items in the datasheet that will help you get better values (expected voltage offset errors, linearity errors, etc.) but the method above will give you a starting point.