The easiest way to download the Feed the Beast launcher is via Feed-The-Beast.com, which offers safe download options in .exe, .jar, and .zip formats. It can also be downloaded from Softonic's website.
The official Feed the Beast site is the best resource for downloading FTB-related mods and launchers, as it is a dedicated site with instructions and minimal interference from third parties. The Download Now button on the front page brings up a choice between a executable file that can be run directly or a .jar or .zip file that can be extracted later.
After downloading the launcher, individual mod packs still need to be downloaded. This can be done from the Packs section of the site, where different selections of mods can be chosen and installed, such as FTB Infinity and FTB Lite. The packs can then be loaded into the launcher and played. Multiplayer server versions of the mod packs can be directly downloaded from the launcher itself.
If the official Feed the Beast website cannot be accessed for some reason, then the launcher can also be downloaded from Softonic, but users must ensure that the correct download link is used as ads sometimes try to emulate the link.