5 Answers

My hand writing is not very good, never has been. However much I try I can't make it look neat, I don't think it's going to improve now. The person with the worst hand writing I know of is the wealthiest man in our village, he's the Lord of the manor, the local land owner, his writing is almost unreadable, and he had a private education with all that goes with it. The point I'm making is that even a good education doesn't make you write any better.

Read everything you can get your hands on: books, magazines, the back of cereal boxes, receipts, scripts, anything to do with real life………..

If you mean HANDwriting, stop by an elementary school and talk with the primary grade teachers about giving you some handwriting handouts to practice.  A bookstore should also have materials about handwriting.
If you mean your creative writing, start by writing letters, or a journal, in which you describe your day, morning, afternoon, evening, or by hour.  That will help you get in the habit of chronology, putting things in order.  Get a dictionary and thesaurus, so you can substitute synonyms for everyday words and improve your vocabulary.  
Taking a basic English course, or a writing class will also MAKE you write more.  If you let your instructor know ahead of time what you want from the class, (s)he may provide some one:one instruction; take advantage of any extra help you can get. 
AND, everyone's answers here are good advice for you.  GOOD LUCK!

Read a lot. Read the type of books, blogs, magazines you would like to write like. Read some of answers people write here at AKAQA. And take a writing class. I take classes whenever I have time.  Write notes and letters to friends and family. Start writing in a journal about something that interest you.  A lot of writing is motivated by what interest you. Good luck and happy writing!

Might want to start with your grammar and spelling.  Not that I am a spelling champ or have any real skills at writing or grammar. :)  Just an observation.