I already have DLC 1 & 2, and i saw that the DLC 3 & 4 are already avaiable for downloading

I downloaded the DLC 3 and i saw that they have the maps archives (mp_xx_ss.ff and mp_xx_ss_load.ff) and iwd's (iw_29.iws and iw_30.iwd). But, there's another archive, "DLC#3 - Chaos Pack.iw5dlc"

What should i do with this archive?

note: i saw a explanaiton on the "Store" Website but i didn't understand what to do yet.

That's not a archive, or it shouldn't be. That's the installer for the DLC that you can use.

That's supposed to install all the dlc, if you did it manually, that's fine too.

ok i understood now

lock it please

When you run LaunchIW5M.exe, the file should be associated with IW5M, and you can double-click on it to install.