Add the total of the cash amount plus the franking credits to your assessable income.
Corporate tax rate is currently 30% so for fully-franked dividends:
Assessable income = cash dividend / 0.7
Franking credit = assessable income - cash dividend
Example:
You receive a cash dividend of $700
Dividend notice advises 'franking credits' are $300
You report your income as $700 + $300 = $1000
Even though you only received $700 in cash!
Calculate tax at marginal rate (say 41.5%) = $415
Report the 'franking credit' as a tax rebate on tax return
You receive a tax rebate of $300
You only pay an extra $415 - $300 = $115 in tax
Total tax received by government is $300 in corporate tax plus $115 in personal income tax = $415 = 41.5% tax