‘Use‘ as defined by FM is: ‘the working of the organism in general, bringing into action the different psycho-physical mechanisms.’
‘Self‘ means your body and your mind. Indivisible.
Example: You are talking to someone, perhaps utilizing hand gestures. Instead of referring to this as the way you talk, it would be more accurate to say, ‘the way you Use Your Self while you are speaking.‘
The Use of the Self, then, is the way I react, with the whole of myself in any given situation.
Explore Use of the Self the next time you are in a conversation. Note your habits as you talk and listen. Do you gesture frequently? How do you indicate you are listening attentively? Do your eyes crinkle up when you smile? Is there a part of you that tenses when in conversation?
No need to change anything. This is the start of being an observer, honing self-awareness, integrating mind with body.
(Mr. Alexander’s book, The Use of the Self, is the one I would recommend you read first, if interested in the Technique as described by its creator. For a general introduction, read Michael Gelb’s, Body Learning.