How is Lady Macbeth's power shown in Act I, scene 5.techniques used etc.
As it is in many relationships, Lady Macbeth's power is gender-specific: she controls the emotional privately. The Macbeths' relationship is segregated: he is the worker, and she is the home support. Whereas Macbeth is the public servant, Lady Macbeth is the private domestic. Macbeth knows what he wants: to be king, but he doesn't know how to get it. Lady Macbeth gives him the plan (murder Duncan), and in a highly-charged emotional speech, convinces him to act on it by calling out his manhood.
Hie thee hither,
That I may pour my spirits in thine ear,
And chastise with the valor of my tongue
All that impedes thee from the golden round,(25)
Which fate and metaphysical aid doth seem
To have thee crown'd withal.
Lady Macbeth plays upon the segregated and sexist gender roles their marriage exhibits. There is certainly a division of labor that she resents: she wants the power of a man. She knows she cannot attain it publicly as a Thane: she cannot wield a sword and kill. But she can attain it by proxy, through her husband privately by controlling his emotions: giving him the courage and impetus to help her attain power, the crown as well.
I'll just add a bit to mstultz72's excellent answer above, concerning Shakespeare's Macbeth.
Lady Macbeth's power, in this situation, comes from the fact that she does not possess the scruples that her husband does. When he has second thoughts about killing Duncan, she will not. She is more ruthless. She cares less for the possible consequences. She never mentions anything about the possible spiritual consequences in the afterlife, as Macbeth does, for instance. And she does not care that Duncan has treated Macbeth well, or that others in the country have recently developed a respect for and liking of Macbeth, as Macbeth does. She will not change her mind about killing Duncan. This gives her an evil power over her husband and, as it turns out, Scotland.
Of course, while her lack of scruples and concern for consequences definitely leads to her husband's assassination of Duncan, she is not so resistant to "good" as she first appears. She is unable to kill Duncan when she has the chance (because the sleeping Duncan reminds her of her father), and ultimately commits suicide as a result of her feelings of guilt.
Lady McBeth already has more power present in her relationship with her husband. She gets the letter and right away begins pleased and ready to plot the kings death so that Macbeth can rule. She reassures her husband that she will deal with the situation and for him to leave it to her.
For a woman of Macbeth's time, there was usually not that much power as she takes unto her hands. She has a strength over her husband and uses it to yield what she wants. She has red the witches prophesy and she wants to assure that it happens as fast as possible leaving nothing o chance. Yes, she does display her power.