You must complete the initial application process for a Grade 2 General Work Visa from outside the UK, more precisely than your home country.
You must first complete the online application on the UK Government Official Website. The online application form includes questions about your basic information and the purpose of your trip to the UK.
In the second step, prepare all the necessary documents for applying for a UK public work visa. Note that depending on your country of residence, you may also need to have a TB test and obtain a criminal record certificate. It is also necessary to pay extra for health.
Finally, if this is your first visit to the UK, you will need to make an appointment at the nearest UK application, embassy or consulate in your home country, where you will need to provide biometric information and a photo of yourself.