Components can only be added to an item if the item group settings allow for this. Go to  Administration >  Settings >   Items >  Item groups to edit the group settings. You will need administrative rights to do this.

1. Go to  Items >  New and select your company (if applicable).
2. Select an item group which allows for components. The new tab  Components will appear in the side navigation.
3. Go to the new  Components tab in the side navigation.