You must link nodes to enable data to flow from one node to the next.
You can select the link mode in one of three ways:
Select the node (either in the project tree or in the workspace) and click the right-hand mouse button to display the context menu, then select the link command.
Alternatively, select the link mode command from the mode menu.
Alternatively,
click on the link
button 
on the controls toolbar.
To link 2 nodes:
Quick
link using the context menu:
the selected node is the first node in the link, so WITNESS Miner
displays a symbol 
next to the cursor, indicating that you must click on the node that
is the second stage in the link.
Other
link methods: WITNESS
Miner displays
the symbol 
next to the cursor, indicating that you must click on the node that
is the first stage in the link. Once you have clicked on the first
node, WITNESS Miner displays a symbol
next to the cursor, indicating that you must click on the node that
is the second stage in the link.
When you have clicked on the second node, a line appears between the two nodes (indicating the flow of data) and WITNESS Miner returns to normal mode.