PMD editor is a separate program and only in Japanese.You can get the latest version here http://www9.atpages.jp/~mmdaccessory/uploader/index.php?page=1 [879.zip]
PMD Editor is an application for MMD (Miku Miku Dance) where you can edit the models
use pmd editor you can get it on youtube or vpvp wiki
you need pmd editor (and several tutorials XD)
Sadly both of those answers are no. Update - Previous answer is wrong, there is a english version thanks to a user from Deviantart, she translated it. http://showmo456.deviantart.com/ Edit: the webpage above no longer works im sorry about that :-/ Actually there is an English version of PMD and all you should have to do is search VPVP wiki and then look around on there and find the version. Mine says this: PMD Editor (English) Ver. 0.0.6.3 // Translation Ver. 0.1
Im sorry you can't change the clothes in Miku Miku Dance you have to download the PMD editor (don't download the English version because it doesnt work xD) You can find some tutorials on how to edit the clothes (too hard to explain on here)
You use the PMD editor to make any model that you want, you can also edit other models like their hair or clothes but be careful some people don't like it when others edit their models like Nanami or like Anomaro who may let you if you ask him. You can also use a program called metaseq but 3d modeling is hard.
VPVP wiki
Miku MIku Dance (MMD) is a 3D animating programm., witch is used to make models dance, pictures or even to make short movies.
Youtube "Miku miku dance"
yes it does :)
You can use Blender, and then get the PMD plugin to convert between blender and pmd formats. This is useful for bone rigging for PMD, because it's hard to rig bones in PMD editor in comparison to blender. I'm planning on making models this way. There's also metasequoia, but the free version is quite limited, and I have no idea where to convert it directly to pmd file because you have to convert it .x file to upload into PMD editor and make it .pmd.
It's freeware. Google it.