First you need to take a voltage reading at the battery with the engine not running.
Then take a voltage reading at the battery with the engine running.

If no change or less voltage the alternator is not charging the battery.
If you get higher voltage (13.5-14.5) the alternator is charging the battery.

If it is not charging try running a jumper wire from the POS + post of the battery to the light green wire with a red stripe at the back of the alternator (you may have to stick a pin in the wire to make connection as the wire goes into a plug).
Now take another voltage reading at the battery with the engine running.

Does it charge now?
If so and it did not before you may have a bad Instrument Cluster.

If it did not charge you need to check the 14 Ga green fuse link going to the battery side of the starter relay from the alternator. The wire from the fuse link to the alternator may be a black wire with a orange or red stripe.
To check a fuse link just try to stretch it and if it stretches it is bad.