How to remove the piece..any instructions?

I'm not worried much about waterproofing, as I doubt mine still has it intact. I've replaced the screen twice already now

help me.. help me..
i root my C6833 with kingroot, and success... but when i restart the phone, it keep boot loopn and restart. i try to press power & -volume or power & +volume, but not thing happen.

can anyone suggest to me, what i need to do. i really nob about android

reflash mean, fresh..? all data will be delete?

can you guide me? i already have
1. flash tools
2. C6833_14.4.A.0.108_1275-9426

so, can i reflash if cannot boot to android (power & -volume)?

this is preview from my flash tools

09/057/2015 11:57:07 - INFO  - Flashtool Version 0.9.19.10 built on 04-10-2015 21:00:00
09/057/2015 11:57:07 - INFO  - Executing search strategies to find proxy selector
09/057/2015 11:57:07 - INFO  - No proxy found for IE. Trying next one
09/057/2015 11:57:07 - INFO  - Proxy found for firefox
09/057/2015 11:57:07 - INFO  - Syncing devices from github
09/057/2015 11:57:07 - INFO  - Scanning devices folder for changes.
09/057/2015 11:57:16 - INFO  - Pulling changes from github.
09/057/2015 11:57:17 - INFO  - Devices sync finished.
09/057/2015 11:57:21 - INFO  - Device disconnected

and the, should i choose flashmode / fastboot mode?