I have added a few content types in a Content Type Hub site collection. I am am unable to see this content types in another site collection. Is there any setting that I should enable so that the content types created in content type hub can be used in other site collections?
Two things to make sure:
Make sure you have published the content types in the hub (as described here)
Run the timer job called "Content Type Hub Subscriber" for the web application that the site you want the content type on belongs to from Central Adminstration.
Note: This is not possible in Office 365 (SharePoint Online), since you can not manually run timer jobs in this environment. Instead, here patients is the key (wait for it to run).