First you must prove the repairs and upgrades you will be conducting, along with accurate quotes. The lender will then need to agree that those changes do increase your home valuation, and further, send you an approval for the revised appraisal.
During the renovation you will need to pay out of pocket, but once it is complete, you will be reimbursed with the funds according to plan. Keep in mind that many lenders will want the renovations or upgrades completed in a 90-day period.