Prepare an image, give it cyan background and save as .bmp. Open Era Start Menu and click
def editor. In "type" choose $43 Adventure Object. Go to frames, find your image, add it and check all special colours that are present on your image. Go back to "General", tick "Make Msk and Msg", "def path" and browse place for saving your def. Press a big button with a monkey wrench and voila! your def is ready
Now open MMarchive, create a new .pac file, add your def files along with .msk and .msg. Create a new folder in "Mods" directory (give it a name of your mod), make "Data" folder and save there your .pac file. Make another folder in "Data", called "objects".
You also have to make a .txt file with a parameters of your new objects. Open Objects Editor In Era Start Menu and fill all necessary fields. Press Ctrl+E to add labeled objects. After all save .txt in "Objects" folder.
Now go to Mods Manager in Era Start Menu and enable your mod. If you've done everything correctly and I didn't louse something
you should have your own working mod now!