The answer depends almost entirely on one thing: whether your country of origin appears on the DVLA's list of "designated countries" with licence exchange agreements.
The designated countries list
If your country is on this list, you can usually exchange your licence for a GB one without sitting either the theory or practical test.
If your country is not listed
In that case, you will need to apply for a provisional licence and pass both the theory and practical driving tests, just as a first-time learner would.
Partial recognition
- Some countries are listed only for certain vehicle categories
- A test may still be required for categories outside that agreement
It is worth confirming your country's exact status with the DVLA early, so you can plan realistically for test preparation if needed.