Navigate to websites like Onlineshorthand.com, Angelfishy.net and Omniglot.com.
Compare the passage you want to translate with the examples that are provided of the different shorthand systems. Study the first sentence of your transcription and try to identify letters or diphthongs that clearly match one system.
Visit your local bookstore or websites like Amazon.com or Barnesandnoble.com to find a book on the system of shorthand you've identified. Teeline Fast by Ann Dix, The Gregg Shorthand Manual Simplified by John Gregg, Louis Leslie and Charles Zoube and Course In Isaac Pitman Shorthand by Isaac Pitman all provide comprehensive information on the symbols that make up each system.
Go through your shorthand transcription word by word, using your reference book to translate as you go. If you have trouble making sense of some passages, you can use the context of other words and phrases to make sense of any problem areas.
Read through your translation and use context to tidy up your work.