How do I install imovie plugins?

Question

Do I just drag them into the imovie plugins folder?
And how do I access them? ie will they appear in the imovie Titles/Transitions/Video Effects tabs?

Answer 1

Yes ..and Yes.
(..But some Plugins arrive as compressed files (possibly with the suffix .dmg or .tar or .gz or somesuch), which should automatically un-compress themselves, and it's the resultant uncompressed item which needs to go into the iMovie Plugins folder. Occasionally, the compressed files don't automatically uncompress themselves, so you may need to double-click on the file to start the un-compression routine. Additionally; some - well-written - plugins automatically do drop themselves into the iMovie Plugins folder by themselves ..others have to be manually dragged there. If you see something with an arrow which seems to be saying "drop me in the iMovie Plugins folder", then drop it there manually.)
HOWEVER, be aware that (a) some iMovie Plugins which were created for earlier versions of iMovie may not work correctly with iMovie HD 6; and (b) iMovie Plugins written for 'PowerPC' processors - previous to Macs moving to Intel processors - may force your Mac to run iMovie via the 'Rosetta' PowerPC emulator, instead of running it as a proper Intel application.
These two considerations mean that..
(a) some 3rd party plugins may not work properly (written for a previous iMovie version)
(b) some 3rd party plugins may not work properly (written for PowerPC processors, instead of being the latest 'Universal' plugins which work with both PowerPC and Intel processors).
So as long as you were careful to download only plugins which say that they work with iMovie 6 (..or "iLife '06"..) and are 'Universal' and therefore work with Intel processors ..then everything should be OK.
Even if your plugins are not Universal, if they're for iMovie 6 they should work, but iMovie may run a bit slower, because instead of the Intel version starting up, the PowerPC version may start, and ought to run under the 'Rosetta' PowerPC emulator. (No message will appear to say that it's running under Rosetta: the process is "invisible".)
Phew!
In all probability everything will be fine, but if it's not, either (a) or (b) above (..or both!..) may be the reason why not!