Tiger Salamander Temporary Home

As I had posted yesterday, I recently took in a young Tiger Salamander from a friend who was unable to care for him anymore. I am COMPLETELY new to owning any type of amphibious pet. After making sure he was, in fact, a Tiger Salamander I was advised to remove him from his aquarium and put him in a proper tank with substrate. I will be getting a larger tank in the near future but for now he's in a tank with the same width and length of a 10 gallon (it's length is about 3/4 of that of a ten gallon). Is this an okay size? I also added some "Tropical Soil" made from coconut fibers as directed by many Tiger Salamander websites. I put him in his new home with a shallow bowl of water to submerge himself in and watched for a couple minutes to ensure his new home would work for him. I noticed his skin started drying (the coconut fiber is moist) and he immediately dove back into the water. What can I do to help him adjust to his substrate? By the way, this is just a temporary setup until I can get him a proper hide, water bowl, and a larger tank.

I apologize for the second picture, I realize it probably isn't too helpful. I'm just extremely worried that I'm going to mess up and hurt him.

Here's an article that should get you started!