need some help

how do i put objects together/link them to make more complex one,s

Select the objects you want to link together in one of two ways (That I know of anyway... there may be more):
1) Shift-click on them one at a time while in edit mode, leaving the one you want as the "Root" or Parent prim to be the last one. This is the method I use the most, but I am a control freak.
-OR-
2) While in edit mode, frame them with a select box by clicking and dragging to the opposite corner of the collection. Keep in mind that this method gets EVERYTHING in range of the window, so it is best to do this looking down from above (otherwise, you risk trying to attach your stuff to your neighbor's house... or the boat out at sea. You can't really do it, but it can generate some sprectacular errors.) Note: This method takes some practice, is prone to erros and has less control over the selection of the parent prim, but it does have its uses, like when you are trying to get at one prim that is inside another, but don't want to move the obstructing prim...

OK... Once you have all your prims selected, you go to the Tools menu in the menubar and then select "Link"

Voila! If you haven't tried to link things that are too far apart, and haven't tried to link to your neighbor's properties, and managed to get all of the prims (even the little ones) together and not forgotten when you were selecting, you should now have a linked object...