Since you are trying to find out how to install couchdb, you must have already researched about Couchdb.
Its pretty easy to install couchdb using ubuntu package manager, no need to compile from source or anything.
just type in this command for prosperity :)
sudo apt-get install couchdb
To test if the couchdb has installed properly.
Just try the URL : http://localhost:5984
it should return something similar to: