"Showing, not telling" is one of the hardest yet most useful techniques you can learn in writing.
As DarknessofHeavenandDreams said above, don't infodump. "Showing, not telling" basically means using actions, dialogue, senses and so-on to tell the story, rather than using the short-cut of just explain everything to the readers in a simple sentence/paragraph.
Example:
- Darren had brown hair and blue eyes.
to
- Darren ran a shaky hand through his brown hair and eyed Sammy with concerned blue eyes.
OK, that's a terrible example, but you get the idea.
Another example (sort of); a few weeks back, I wrote a collection of short-stories based around a character called James, who had a daughter named Jasmine. Now, rather than saying:
- Jasmine was James' daughter.
Instead I used dialogue like:
- "I have to pick Jaz up from school later"
to make it obvious that James was most likely her father. (Not exactly what I wrote, but close.)
Or, rather than saying:
- Mike had kidnapped Ian's children.
You could use dialogue, like:
- Ian grabbed his wife by the shoulders, "He's got our children, Julie!" he shouted, "Your scum of an ex-husband has our children!"
Little things like that can make a story more natural, rather than forced and like you're trying to force infomation down the reader's throat.
In the end, it's all about practice, practice and practice and eventually it will come second-nature.
Good luck.
(Also, I would recommend The Road to Somewhere: A Creative Writing Companion by Dr Robert Graham, Dr Heather Leech and others which is extremely helpful - though it may be slightly pricey - but we've been using this book in our Creative Writing course at University and I've found it very useful.)