I used to update the inputs.conf for ingesting new folders and logs in splunk forwareder, but is there a way to add data to splunk forwarder from UI , from splunk main UI. ?
It is not possible by design. Forwarders are not supposed to have web-based GUI. They should be configured through a configuration/source management tools such as ansible, git, etc. or with a Splunk Deployment Server. You can configure manually through the CLI but there is no GUI for forwarders using the Universal Forwarder installation.
the Universal Forwarder has no UI
if you are using Heavy Forwarder, you can navigate to settings -> data inputs and configure from there
how about making forwarder as deployment client?
sure, for Universal and Heavy Forwarder (or any splunk instance) you can use CLI or edit files directly, described here:
http://docs.splunk.com/Documentation/Splunk/6.5.3/Updating/Configuredeploymentclients
on HF you can use the GUI