I found this helpful when trying to annotate some blocks with OD
Here is the link
1- 'mapanntemplate' (don't enter the quotes - you'll get a dialog box, when you hit ok, it'll open the block editor)
2- 'mapanntext' (then I hit 'enter' for new text. You'll get a dialog box asking for infomation for you to supply for the label. Under the 'value' box, you can specify a field from your object data to be supplied. When it asks for the insertion, i always use 0,0; which inserts the text right where i need it inside the polylines.). At that point, i close the block editor, saving my changes on the way.
3 - 'mapanninsert' (check the template you created, select your polylines, and voila! Labels!
if the labels need to be tweaked, use the 'mapanntemplate' again, to edit the template contents, such as size, layer, etc.; then run the 'mapannupdate' command to have those changes reflected.