My impression is that the align tool only works if two or more objects are selected to line up to each other. However, you can right click on any object, including text frames, and choose “Position and Size.” When aligning to page, it’s often a good idea to set the Anchor to “Page.” By default it is typically to “Paragraph.” To Page allows it to move more freely in some cases. In the “Position and Size” dialog, you will see the text frame’s horizontal and vertical position. If you want to align to left of page, Choose “From Left” and enter 0. If align to right, "From Right, and enter 0. Similar to align to top and bottom. It’s not as quick as using the align tool, but unlike some programs such as Inkscape, there doesn’t seem to be a checkbox for “relative to page” within the Align dialog.
An alternative to the right-click for accessing the Position and Size dialog is to find it here in the menus: Format → Text Box and Shape → Position and Size.
Hope that helps.