To open Item Maintenance in SMS Pro, click the "Maintenance" button at the top of of the screen in the blue bar. 

Next click "Item Maintenance [Price Only]"

This will open up a "view". A view is just a memorized screen layout. The boxes you see on the screen can be arranged in whatever way you'd like, then saved that way so it opens up like that every time you open it. You can have as many views as you'd like. 

Explanation of the buttons on the top of each table

1. Exit button: This will close this table
2. Undo Changes: This will undo whatever change you made to that record 
3. Apply Changes: This saves the change you made to that record 
4. Delete Record: This will delete the record of whatever table you're working on. *NOTE* this doesn't delete the whole item, just the table you're working on at the time. Ex: You can delete the price table record, but that won't destroy the whole item. 
5. Add record: This will add a new record on whatever table you're working on. Ex: You might add a second price record to an item. 
6. Less Details: This will shrink the current window you're working on exposing fewer details of that table 
7. More Details: This will expand the table you're working on to show more details 
8. Global Apply: The global apply button applies the changes you've made to a specific record to all items in the browser window. This is the mass change button. It's sometimes referred to as a tornado button because it kinda looks like a tornado. *NOTE* This is an advanced feature and should be used with care. You could potentially make unwanted changes to dozens or hundreds of items by mistake if you aren't careful.