1) Click the "Add Sprite Definition" button at the top of the Graalshop program (looks like an explosion)
2) On the left side of the add sprite menu, in the Image field, you need to name the attribute you wish to use.
3) In that field, type in "ATTR1". You can replace the 1 with any number from 1 to 30, like "ATTR20".
4) Now that you have decided which number your attribute is going to be, you need to pick the description and index you want.
5) Then you need to set your sprite size and such, if you don't know how to do this, I can explain this later.
6) Then you click the Add button.
7) Now the attribute isn't going to show up in Graalshop, because you haven't set the image yet. So save the gani, and close Graalshop.
8) Now right click the gani FILE, and select "Open With" then choose a text editor (I use WordPad) and open the gani file with the text editor.
9) Go down until you see the "DEFAULT" area, and underneath the last one (usually like DEFAULTBODY body.png), add the line "DEFAULTATTR1 imagename.png" (1, or whatever number you chose in step 3)
10) Save the text file, and reopen the gani in Graalshop. You should now see the default graphic in the left scroll field.
I guess that should explain it all, if I missed something or you're having trouble still, just tell me what the problem is and I will solve it for you.
edit: By the way, if you're only using a couple ganis, you can just use gani's 1-3 and you can edit the gani fields in the right side of Graalshop instead of doing it via text editor.