Where do I claim renovation cost for in home office expense

Assuming you are claiming home office expenses for a Schedule C business, it depends on how you calculate your expenses. 

If you are using the simplified square footage method, renovating the home wouldn't change your deduction unless you change the total square footage and home office square footage.

If you made renovations that qualify for the special energy-efficient home improvement credit, you can visit that section under Deductions & Credits.

If you made repairs to your home, enter them as direct (affecting the home office) or indirect expenses (affecting the whole house).

If you made significant improvements to the house, you can enter them in the Assets and Depreciation section.

Please see Cynthiad66's response in this thread for more information.

See here for more information from the IRS on this topic.