LOCK ITEMS
To lock items, go under the Organize tab of your toolbar :
1 Select your item and click on the lock icon 
.
2 Once locked, you will not be able to select it or modify it.
3 To unlock your item, click on the unlock icon 
.
GROUP ITEMS
Grouping items allows you to do the same actions on multiple items:
1 Multi-select items (with your mouse or by pressing CTRL on your keyboard and selecting items).
2 Under the Organize tab of the toolbar, click on the group icon 
.
Your items will appear in red and you will be able to move and duplicate them simultaneously.
3 To ungroup items, click on the ungroup icon 
.