I've been playing Destiny for a few weeks now, but am still nooby, I don't understand a lot of things, but I'm really confused on what I should do next as I can't do the misson that requires friends, help?
If by "I don't have friends" you mean you don't have PS Plus or Xbox Live, then you are out of luck. You need those services to do almost everything in Destiny.
If by "I don't have friends" you mean you don't have a big friends list (or people who play Destiny), most activities have Matchmaking. They are:
The Heroic Strike Playlist (you can get up to 390 light gear here)
The Level 42 Prison of Elders (NOT Challenge of Elders, you need to form your own team for that)
Any Crucible playlist except Trials of Osiris
Activities that you NEED to form your own team are:
Any of the 4 raids
Challenge of Elders
Trials of Osiris
Just select an activity that has Matchmaking (it will tell you so) and have at it.