Hi Shraddha,
AutoAnnotate is not installed automatically when installing just EnrichmentMap.
If you install the "EnrichmentMap Pipeline Collection" then that will install EnrichmentMap, AutoAnnotate, WordCloud and clusterMaker2.
It's also recommended to install the "yFiles layout algorithms" app because the yFiles organic layout is now the default layout when creating an EM network.
The easiest way to install an app is to first start Cytoscape, then go to the app store page for the app, then click the "Install" button. If Cytoscape is running it will install it in the right place automatically.
To manually install an app jar file that you downloaded, copy it to the <user-home>/CytoscapeConfiguration/3/apps/installed folder.
Hope that clears things up.
Mike.