Beginner schefflera abricola bonsai help

[Meanmrmurph]

Okay so last night I bought a umbrella tree at lowes and a pot and planted it but I want real soil for bonsai what is the best ingredients I could buy from storesstores please help. And I want it to have aerial roots so I put a plastic bag around it and mist it. Please help on the soil right now I'm using what it came with

[Meanmrmurph]

heres some pics I noticed the stem kinda looks shriveled...any advice sorry my grammar/spelling was bad I was in a hurry.
https://www.flickr.com/photos/29485656@N ... 852516774/