I have created a custom page called training.pt. I want to add it into the plone's default navigation . How to do it. I have the file on my custom addon in the file system. Kindly help me with this query
Hi,
Is "training.pt" the BrowserView/Template for you custom Contenttype?
Did you install your Addon (/prefs_install_products_form)?
This part is maybe you asked for https://training.plone.org/5/mastering-plone/views_1.html
Maybe you should make the whole Tutorial @ training.plone.org 
yes but it is not displaying in my navigation bar
If you mean your custom content-type to appear in the navigation go here and mark it:
plone_site/@@navigation-controlpanel
It is a template page not content type. Anyway thanks for the reply
If the contenttype installed without errors and you created a content with your type, maybe the PageTemplate contains some errors...