First, I would like to know if you are actually asking about the actual accent of the British Nation or the actual skill of speaking English. But I'll try to explain this first, the skill of speaking English could not be learned but must be practiced. Reading books and writing essays and such others could help you get familiar with the language. Most of all, speaking repeatedly in English could help you enhance this particular skill. But if you want it the easier way, then hire a speech coach to help you out.