How to use MinGW-64 with Qt Creator

I am aware that there are many post about this, but I honestly didn't understood any of it.

So, how do I install a kit for my Qt Creator (open source 5.7)?

• I already downloaded and installed MSYS2.... don't know what to do with it.
• I already downloaded and installed Qt64 - NG.... no clue what to do next.

I just want to be able to develop in Qt and chose betwen MinGW 32 and MinGW 64.

Thanks in advance!

EDIT: I also checked the wiki page. Most of the commands didn't worked. And I was told that it is outdated.