Yes, you can use Replace field contents in the records menu to do this. Make a back up copy first before trying it out as this will modify numerous records all at once.
Often, the need to copy a value from one field to many others indicates a need to redisign your tables and or relationships.
Thanks PhilModJunk. Haven't quite mastered tables and relationships yet. What's the best way to learn how?
There are books and tutorials as well as forums like this where you can ask questions.