Getting custom doodads to the editor

hey im sorta new to the editor and have no clue how to bring custom doodads into the editor. i want to use the legless table to make a suspended bridge. Please help me ^_^

For the legless table, just import the mdx file and set something's model file to the imported file, I didn't even have to restart the editor for this one.

Since your new to the editor, Ill be more specific on Terrain guys advice.
-Open Editor
-Open Object Editor (Little helmet icon)
-Import mdx file where ever you saved it
-Scroll though the long list of stats for that object and assign a model file that is simlar

thx.....it worked