Hi I need to display posts in a category on my page template. How can I do this? Thanks
Just take a look at the WordPress Template Hierarchy.
You'll find out that WordPress has three different types of templates, that you can use:
A) For built in taxonomies: Category & Tag
B) For custom taxonomies.
The template engine will search for such templates when you request a category/tag/custom taxonomy archive page.
The excellent diagramm by our man Chip Bennet.
I'm reading this to say you want to add a list of category posts on a page view, not a single post view. That being the case I would first suggest looking at one of what I imagine are numerous plugins that can provide this functionality.
An example plugin would be BNS Featured Category* which provides a shortcode that should accomplish what you are looking to do.
*NB: Full disclosure, I wrote BNS Featured Category.
Try using child theme. Create a custom template and try the following code.