1. Click on "Proposals"
2. Select the Proposal of Your Preference
3. Click on "Add Optional Item"
4. Fill The Information Required
5. Click on "Save"
6. Now Your Optional Item Should Appear
7. Click on "Customer View"
8. See This Optional Item on Your Customer's Proposal
Your customers will always be able to add it or remove it, and this will affect directly on the total of the proposal
