My husband got a bonus of about 25000 on which about 7k tax was deducted by his office. Where do I need to mention this bonus in tax return?

You do not do anything special about the bonus on your tax return.   You just enter the W-2 and allow the software to do the calculations.   There is no special tax or tax rate applied to a bonus. on your tax return.  What matters is the total amount of income and the total amount of tax withheld.   All of the other variables such as filing status, dependents claimed, deductions, credits, etc. will also be used to determine whether you owe more or get a refund.

The bonus and the tax should be included in his W-2. The bonus should be included in the total wages in box 1, and the tax that was withheld should be included in the total tax withheld in box 2. If they are included you don't have to do anything special. Just enter the amounts from the W-2. It doesn't matter that it was a bonus. It's just treated as additional pay.