don't ask me why it's greyed out, but I agree, it's very weird (and frustrating)...
1) Insert Object (in Manage ribbon) - use that to insert a Paintbrush Picture (or whatever you find works best)
2) create a new symbol (symbol button in Define group of Manage ribbon) - here you can use the traditional insert image button. Place your image in the symbol and finish the sketch, giving the symbol a name. Switch to the Annotate ribbon and click the "user" button in the Symbol section, select the name you've just saved and place the new image symbol in the idw.
Hope that helps.
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Lithium - helping nntp users with mania, depression and headaches