If you are currently not in design mode, please enter design mode by clicking on the blue snowflake icon in the upper right of the Inspire software, making it Orange to enter Design Mode.
Design mode OFF:
Design Mode ON:
In design mode, you should have the ability to select the text object in question, which will bring up the marquee handles and tools, one of which will be the Object Edit menu from which you can unlock or re-lock the text object. Alternativley, you can use CRTL + SHIFT + L while the object is selected to lock or unlock the object. (in OS X, the shortcut would be COMMAND + SHIFT + L)
Also, from Inspire’s Object Browser, you can select the object in question, then double-click on the lock under the ‘Locked’ column to bring up a drop-down to toggle the object between locked and unlocked states.
Be advised that if the flipchart in question had been Published by its original author, you may not have the ability to unlock or otherwise edit any objects in that file.