Install the 3.5 inch hard drive on the thermal take H200TG unit.
Install the 3.5 inch hard drive on the thermal take H200TG unit.
Check the manual for proper placement details. The guide mentions support for two 3.5-inch drives, but you found only one available.
The manual describes installing two hard drives: one screws into the top of the bracket via its bottom holes, while the other fits inside the bracket and is secured by side screw holes.
35HDDinstallation.pdf from thermaltake.com featuring a single exterior and an internal mount
Find a way to reach the hard drive bay you installed, but you're having trouble taking off the bottom cover.