Hi. No expert as such. But start with a story like for a book. Without a story you have nothing anyway.
Classes in English Literature will give you pointers in the right direction. There will be adult classes at the local further education college, or they should be able to let you know who does them.
And try drama school! What better way to learn how to write a script than learning how to follow other peoples work and act from these.
...As they say for luck in the theatre, or used to "break a leg",