Yes you need to install Couchbase on each node of your cluster, but you configure the “cluster” on a single node.
Once you have install all the nodes and configure the cluster on 1 node you can “add” all the other nodes to the cluster. You can do it either from a configured node or from a new node.
During this phase you will have to enter the Administrator username and password.
Here some interesting pointers about Cluster creation and configuration:
1- Create the cluster:
UI : http://www.couchbase.com/docs/couchbase-manual-2.0/couchbase-getting-started-setup.html
CLI : http://www.couchbase.com/docs/couchbase-manual-2.0/couchbase-cli-other-examples.html#couchbase-admin-cmdline-couchbase-commands-cluster-init
2- Add node to the cluster:
UI : Click on Server Tabs and click on the “Add Node” button
CLI : http://www.couchbase.com/docs/couchbase-manual-2.0/restapi-create-new-node.html
PS: You are talking about setting up a cluster over a Wifi network, this is OK for development/testing but for production it is always better to have fast and reliable network, so better with cable/fiber.