Look here:
http://doc.slitaz.org/en:handbook:start
System Administration/Packages
http://doc.slitaz.org/en:handbook:packages

There are two ways to install packages in Slitaz:

1. Use Menu-->Systems Tools-->Package Manager
search for your package, then double-click for install/remove options.

2. Use command line: # tazpkg get-install packagename
Try # tazpkg for a list of options. The get-install option will download and install the package for you. If you already have a downloaded package, you can type # tazpkg install packagename to install.

Thanks chaps. The funny thing is that initially my package manager just said '205 installed, 0 available, 0 mirrored etc' - so I thought the package manager was just for removing packages!

Then, for some reason (I didn't do anything specific that I could remember) the packages leaped to 2500 odd - and I was able to install them.

Then, I rebooted my machine and now I can't access them again. The computer and net browsing and downloading are working fine.

Now, as I type this, I notice I have 2600 odd available apps again! This is a bit odd - does it just takes ages to refresh?

and very strangely, now, the 2 apps I am looking for (tsclient and rdesktop) are no longer in my list...

I can do the command line thing and they seem to work though

I suspect you are using cooking, instead of stable (stable 3.0 has "only" about 2300 pacakges)
If you are totally new to linux, stick with stable 3.0 (cooking is changed regularly and probably its packages too, plus it does not work as you expect from a stable version. I played witht the latest cooking this week end, you do not want to install that, i promise....
Download 3.0 from the slitaz.org main page link

this being said, in the package manager you should first the "recharge list" button (the available packages number will jump from 200 i believe, to 2295)
and the "upgrade all" (though i must admit i am not convinced that that one is always the best idea....)

and, yes, this system is a dream come true ;)

If you run 'upgrade all', there is a high likelihood you will brick your system. If you do, there are couple of things you will need to do to make it work again. 1. change /boot/grub/menu.lst to load the new kernel (I think cooking loads the 2.6.34 kernel by default and the upgrade will change that to 2.6.36, unless the latest cooking iso available for download already provides the .36 kernel). 2. you will need to replace /boot/vmlinuz-... file with a working copy. Take a look at these posts if you run into issues after upgrading:

http://forum.slitaz.org/index.php/discussion/comment/10013/
http://forum.slitaz.org/index.php/discussion/2152/after-cooking-upgrade-no-hardware-drivers-loaded-no-xorg/#Item_19

With regards to the package manager, in general, the graphical package manager is a lot slower than the command line. This, I think, is true for other distros as well.

@ ms3811: you are talking about cooking while i recommended to use stable.

Julian said he is a total linux newbye. Don't you think using the package manager (even if it is slower, which it is) and a stable version is the way to go...

If he's already got cooking installed, figured he could use some help feeling his way around.

I agree, stable is definitely a better choice for someone starting out.

oh i get your point.... ;)
have a nice day