upgrading to 3.6.8

[Deidre]

I'm trying to upgrade from 3.6.7 to 3.6.8
I've read the upgrading instructions, but there is some stuff I don't understand:

- It says you need to install it all over.... do I upload the files in the same directory as my old ones and overwrite them? Or do you upload them in a new directory or what?

- When you edit your config file, do you enter the same database, username and password as your "old" forum (the 3.6.7 one in my case)? Or do you create a new database for it.

- If you use the same database, do you use the same table prefix as your "old version forum"? or something else?

Please reply as soon as possible
Thanks
Deidre