Replace
The replace feature can change a specific field across multiple records. From list view, select the records you would like to change. From the top menu, select "Utilities" and "Replace."
On the next screen you will be given several options on how you would like to use this tool. I believe that it is best to decide exactly what you want the field to say and use the "Replace all values in field option." In the example below the "Edition" field is being replaced. With certain fields, such as Artist, you will be prompted to choose from a definitive choice list. When you have chosen what you want to replace, select "Replace" in the bottom left. EmbARK will prompt a few warning screens to verify your choice. 
In the example below, the Edition field in the selected records has been changed to reflect the replacement.
Apply Keyword
Similarly, keywords can also be applied to multiple records at once by selecting the records you would like to apply the same keywords to and then selecting "Utilities" from the top menu and "Apply Keyword" 
All of the records you have selected will appear under "Object List" on the new screen. Add keywords as described in the Cataloging Manual (Step 8) and select apply. 