You don't.
All Fast Offering donations are automatically swept to Church Headquarters. Any local needs are automatically re-reimbursed from CHQ. Donating to a specific ward doesn't increase the amount of funds that bishop has available. The only thing that counts is that the donation is made.
You may want to read
this thread from 5 years ago.
In addition, the new handbook says (34.4.2):
Members should contribute fast offerings without designating how the funds should be used. Bishops may not enter into arrangements or make commitments to give a member’s fast-offering contribution to an individual or family or to use it for a special purpose that the donor designates.
Have you searched the
Help Center? Try doing a Google search and adding "site:churchofjesuschrist.org/help" to the search criteria.
So we can better help you, please edit your
Profile to include your general location.