Found in Mouse Tools
Use Text Tool to add and edit free-form text comments to a circuit, or to create or edit labels associated with components.
Add a label: Click a component to add a label, which will stay with the component as it is moved or copied. Some components don't support this feature, but most built-in components can have a label attached.
Edit a label: If a component already has a label, click the label or anywhere on the component to edit it. The lower left panel can also be used to edit the label text, font, position, and other settings.
Click any blank area of the background to add a new text comment, or click an existing text comment to edit it. These are intended for documenting your circuits. Text comments can have multiple lines, and can be styled with colors and other properties. Unlike labels, comments aren't attached to a component.
Hold shift to enforce snap-to-grid when adding new text comments. Normally, text comments are not required to be aligned to the grid the way most components are.
Tip: When TextTool is active, the property panel at the lower left shows the default options that are used when creating new text comments, including font, foreground and background colors, alignment, and format (plain, wrapped, or styled). You can edit these defaults, and Logisim will remember your preferences. See Comment for details.