I think you are trying to do a qualified HSA funding distribution -- sorry, that only is allowed for IRAs, not allowed for pensions and 401k type plans. You would need to withdraw the money (or cash your pension check), pay the tax, then contribute it to the HSA, and take the tax deduction. Assuming you are eligible to make HSA contributions, the tax deduction on the HSA contribution will offset the tax on the pension.
But remember, you must be eligible to contribute to the HSA -- that means you have a qualifying high deductible plan and no other medical coverage such as Medicare.
