I have a cluster environment , i want to install a specific add-on from splunk-base to the (5)Universal Forwarder .
How can i do it , is there a way to install it and just deploy it to the 5(UF) or i should install it manually in (5)UF ?
You are looking for the function of forwarder management which can be obtained through the use of a Deployment server
If you do not have a deployment server you will need to install it manually on each forwarder (or use some other type of automated/scripted deployment software)
The deployment server sure can!
Check out these docs for instructions on how to do it