where can I add UK Pension?

You can add it under foreign income.   Search for foreign income and use the jump to link.  You need to report foreign income if you're a US citizen or resident.   You'll need to report all of your income, whether it was earned in the US or abroad.

@mehtjyo50 , because of the  Tax Treaty between US  & UK, the type /source of pension matters  on how to report.  Generally  govt. pensions ( paid from public funds )  are taxable income on returns filed with the payor country.

Private pensions on the other hand may be taxable income for both  countries.

For US purposes you would  report private pensions just as if you had received  a 1099-R.

Does this make sense?   Please answer my questions.

Also are you a US person ( citizen/GreenCard / Resident for Tax purposes )?

Yes, I am.