Your UK residence status affects whether you will need to pay tax in the UK on your foerign income and your entitlement to tax allowances and exemptions.
If you are UK resident for the full tax year, you will need to declare your foreign income in a Self Assessment tax return.
If you are considered not resident in the UK for the full tax year, you will only declare your UK income, by claiming split year treatment on a Self Assessment tax return.
To determine your residence status, you will need to perform the statutory residence test, which can be found here:
RDR3 Statutory Residence Test
You can register for Self Assessment here:
Register for Self Assessment