In Admin area, go to Tools, then Modules, this is were you install Blog, Forum & a host of modules.
Install one at a time, some may fail to install as they are dependent on other modules that have to be installed first, check any that fail to find what modules needs be install first.
Install one at a time, some may fail to install as they are dependent on other modules that have to be installed first, check any that fail to find what modules needs be install first.