@monte, the link to create a new post is located between the lines "Latest Discussions" & "Please Read This Before Posting!", where it says "Topic - Add New »". Click on the "Add New »" to start a new post.
To install packages, you can start the Slitaz Package Manager (usually under Slitaz Menu --> System Tools, although I can't see it my menu for some reason). This will give you a nice GUI to manage packages. Alternatively,
To install firefox, as root, type in a terminal:
$tazpkg get-install firefox
The current version listed in the Slitaz (cooking) repos is firefox-8.0.1. If you are using stable, you may see a different version.
To install flash, as root, type in a terminal:
$tazpkg get-install get-flash-plugin
then,
$get-flash-plugin
(the second command 'get-flash-plugin' may not be necessary since I think the latest get-flash-plugin script automatically does that for you.)
In your last question "can you teach me how to delete and add a directory ?", are you referring to creating/deleting directories in Linux? If so, the commands are (executed in a terminal):
$mkdir directoryname (creates a directory)
$rmdir directoryname (deletes a directory, empty only)
$rm -r directoryname (deletes a directory and all it's contents including files and sub-directories)