Here ya go!I had a quick search but no decent directions how to get there on google maps...

From there, you literally just follow Glowworm Tunnel Rd until it ends. Its a smooth gravel road passing through cleared and developed areas of the forest. About half way up the road, you'll pass Old Bells Line of Rd on your right closely followed by a prominent camping area also on your right. From there, the road becomes a bit pot holed and there are a few lumps and bumps in the road which you'll need to slow down for and take at an angle in your car.
The tunnel pictured is about 1km from the end of the road. At the end of the road, there is a car park and its a further 1km walk (one way) to the actual glowworm tunnel which you can view using a halogen torch only.