You need to create a custom solution if you want to modify components or add new ones.
Before you create a new solution you have to create a new publisher first.
Go to Menu Settings > Solutions
Click New
Add Solution Information
Click Save and Close
Click Add Existing
If you want to import existing components to modify or extend them.
Select Components To Add
Select Add All Assets
If you want to import all assets. Select assets otherwise.
Select to Not Include Required Components
Components Have Been Added
The New Solution Was Created.