You can create trees using a spreadsheet (like Excel or Google Sheets), or any other system that can generate tab-delimited files. These files need to be in a specific format, with specific column headings.
These examples show how to set up a CSV format - check the Full Reference Example tabs in one of these samples:
To import a tree, use the Import tool.
1. Go to My Trees, then click Create New Tree.
2. Select the Import option.
3. Choose the CSV option. Using the drop-down menus select which organization you want to add your tree to and whether you want to create a new tree or update an existing one. Once done choose Import File and select the CSV you want to use. 
You can examine the tree created by importing these examples here.
The column headings in the CSV file are:
| Node | (required) The node number. |
| Title | (required) The title of the node. |
| Question | (required) The text in the question area. |
| Content | (required) The content area of the node. Can be HTML. For email nodes, this is the email body. |
| Success | (optional) The category of the node's result. Can be one of ? N or Y |
| Tags | (optional) A comma-delimited list of tags for the node. |
| Score Variable | (optional) The button click variable for this node. |
| Email To | (optional) For email nodes, the email address or variable for the recipient. |
| Email BCC | (optional) For email nodes, the email addresses for any BCC recipients. |
| Email Subject | (optional) For email nodes, the subject of the email. |
| Email Sender Name | (optional) For automatic email nodes, the name of the sender. |
| Email Reply To | (optional) For automatic email nodes, the reply-to email address. |
| Continuation Node | (optional) For document nodes or automatic email nodes, the node ID to go to after sending the email. |
| Buttons | (required) A list of buttons, one in each cell after the Buttons column header. |
See the example links above to see how the various node types are created.