Basic Steps:
1.Define a lookup, lookups value are for drop-down list items.
2.Create VO, this is used to query above lookups
3.in Page file, Add a messageChoice type item in a region.
4.Drop-down list with static items
Similar Posts
https://blogs.oracle.com/prajkumar/entry/implement_poplist_in_oa_framework
http://newtonapples.com/message-choice/