It would be greatly appreciated if someone told me how to make a theme. I need help with it.
acp>styles and templates
create new theme
See the MyBB Wiki and/or Mods site, there are plenty of resources there that will tell you how to make themes.
Unless you know html and css its a bit pointless trying to do a theme
create the new theme as above.
go to templates and add set call it the same as your theme
then go to your ftp client and create a directory named the same as your theme within the images directory
copy all the images from images to the directory you just created
now you'll have a copy of the default theme you can edit as you pleasse.