"How do I tighten my skin?" There are many concerns that people report as causing them to look tired. Are you wanting to brighten, lighten, tighten, smooth or fill out? Usually the answer is yes to all the above, but I still need to understand what your main concern is.
Overall, skin tightening is a daily request. What can you do? Well, collagen and elastin stimulation are the best ways to lessen loose skin. Why is the skin loose? With age there are many independent and interdependent factors. Bones remodel and cause sinking eyes, nose, cheeks and mouth. Muscles strengthen and are at maximal contracture even at rest. Ligments and connective tissue lengthen. Fat pads atrophy and separate. Once high cheek bones can settle into heavy jowls.
In general, anything that helps you stimulate collagen will help you tighten. Some DIY home items are retin a - retinaldehyde, retinol, retinal, and .1% adapalene gel. These lighten and brighten the skin through stimulating dermal growth. They also encourage collagen production and can ameliorate fine lines. Know that any collagen growth is about the long game. It takes 3 mo to see collagen growth, so commit to regular use, be patient, and use for a long time.
Dermal rollers (at .1mm-.2mm in depth) encourage better delivery of topical products to the skin. Using them can also aid collagen stimulation. There are many YouTube videos on how to do this at home. Mainly stay with serums that can be used with a microneedling and stay with shallow needles to avoid permanent damage.
Thirdly, use sunscreen regularly and for forever. Sun exposure is a large external factor to aging. Protect what you have now, because it can worsen without protection. Use an SPF 30 or greater daily and reapply. Lastly, if you would want faster, noticeable results, consult with a doctor who specializes in skin.
Love YOUR skin and it will love you back. :-)