First the most obvious points to check:
Check that the battery is fully charged AND does keep it's charge. If the battery don't keep it's charge, it means that it's dead: Replace it.
In the mean time, you should be able to use your laptop on the charger alone.
If working from the charger and not on the battery:
Check that the charger is still correctly plugged into the wall or a power strip, AND that the power strip, if one is used, is in the ON position, AND there is current going to the used wall outlet.
Try connecting to another wall outlet.
Check that the charger cable is intact. If the cable from the charger is broken, you need to repair the cable or replace the charger.
If you try to repair the cable, you need a sharp knife and some electric tape. Connect the identicaly coloured whires of the cable toggether. Twist tightly. Secure each whires individualy with electric tape. Secure the whiole cable with some additional electric tape or fabric tape.
Check that the power cable is correctly connected to the laptop.
If, after following those steps, your computer still don't work, please ask again here with a precise description of what you tried and any results or observations you could have made.