Feed the Beast installation guide
1) Ensure you have FTB installed [Download]
2) Place the FTB into a folder
3) Launch the client. From here you will have many options as seen on the top bar and down the left.
4) Ensure that on the top bar you have the "Mod" bar enabled, then on the left of the window there should be a variety of mods you can choose from such as "FTB lite" and "Mindcrack". Click the one you want to play
5) Now look at the bottom right of the screen, next to "Launch" there should be a drop down box, saying "select profile". Click "new profile" and add your minecraft details. NB: Profile name is the name that is saved locally so only you see that name.
6) Now hit "Launch" and FTB should automatically install all the mods and such for the modpack you chose.
7) Play FTB and enjoy!