I would remove all the soil and put it in a bonsai soil mix. In that deep pot it may take longer to dry out or dry out unevenly. The bottom may stay wet, longer. So i would pot in a shallower pot. Like 2-3 inches deep. This also allows roots to grow outward instead of down.
You can use a chopstick to test the soil.
Push it in the soil and take it out. Look at it for signs of dampness- or if soil sticks to the chopstick.
If it appears dry then water it.
Also after a time you may get used to the weight of the pot. Wet and dry feels much different.
A fast draining soil will dry out faster.
When you water. Water from the top.
Let the water run out the bottom through the drain holes- really soak it down. Then let it dry.
This is only for bonsai soil though not for potting soil.
This is your first step- bonsai soil and some osmocote mixed in.
http://wigertsbonsai.com/store/index.php?main_page=index&cPath=68
Watering is just as important as drying and soil choice because the roots need air flow and water and ferts for a healthy tree.
If you get a new pot get one that's like 5 inches by 4 inches by 2 or 3 inches deep. Exact measurements aren't important right now. Make sure it has at least two drain holes. The tree will be unstable at first unless you wire it down. You don't have to do this at first if you feel uncomfortable. If the tree will be inside it will be ok.
If you are planning on keeping this outside then you should wire it in the pot to hold it down.
You will get the hang of it.
Read as much as you can and ask questions here.
There is a lot to learn and this is a nice tree. Good luck
Too!
