I haven't found any "export modpack" functionality built into MultiMC, so you'll probably have to handle that yourself. The simplest way to do it would probably be to zip up your entire instance folder (i.e. <MMCInstallDirectory>/whatever/instances/YoutModpackNameHere... the same one that opens up when you click the "Instance Folder" button in MMC), send that to your friends somehow, and have them drop the zip in their instances folders, and unzip it.
However, there's a lot of stuff in the instance folder that your friends probably don't need, such as saves, logviles, and vanilla MC code. So you might be better off zipping and sending your instances/YourPackNameHere/minecraft/mods and instances/YourPackNameHere/minecraft/config folders, and instructing your friends to create a fresh vanilla MC instance of the proper version, install the proper version of Forge, then dump the contents of the zips into the appropriate folders (mods and config).
Another option would be to look into
QuickMods. I've no idea how to use it, but the linked video should explain what you friends, at least, would need to do. You'd only need to send the configs and a JSON text file; after that, MMC would handle all the downloads on its own.