Are you creating the modpack for your own use, or for a server? If for personal use, follow this video tutorial by DoctorDharok. It's simple and fairly easy to follow. It's very important to make sure everything in your pack is compatible, so take the time to add them one by one and then open minecraft to see if everything works properly before adding the next mod. Be sure all your mods are for 1.7.10, and that Forge is 1.7.10 (chose the "Universal" version of Forge). The only change I'd make to the video tutorial is that I used copy.com instead of Dropbox, because of Dropbox changing their policy for public files. Copy.com is free and very easy.