Select the Text tool, then left-click on an empty place on the canvas. In the opening Text Dialog, you can create and format the text. Symbols can be inserted by the symbol button, and also can be typed if there are keyboard shortcuts for them.
Select the Text tool, then, with the cursor, hover over the text that you would like to change.
When the textbox becomes highlighted in blue, left-click on it.
The Text editor opens, here you can edit your text as you like.
After creation, the textbox can be moved on the canvas by dragging.
Hover over it and push the Delete key or the Delete button on the toolbar.
Click on one text, or encase more than one textboxes in a red rectangle by dragging with the active Delete tool.