To use a wax seal, simply select the seal and color of wax best-suited to your particular piece of correspondence. Then, gently heat the wick on the wax and allow enough drops of wax to fall onto the envelope to cover an area roughly the size of the seal. I usually keep a lighter in my box of quill pens, wax, and seals, for this purpose. Then, blow out the flame, and use the end of the wax to gently smear the wax to cover the area of the seal.
A variety of wax colors. My favorites have a hint of glitter in the wax.
The G-clef and "A" were gifts from my mother. The "M" I purchased on Etsy.
Allow several drops of wax to fall onto the area of the seal, before extinguishing the flame and gently smearing the wax to the area of the seal with the end of the wax stick.
Apply your seal firmly, and for some 5-10 seconds, to the center of the area of wax, being careful to apply it right-side-up. Then, gently rock the seal to one side to be sure that the wax has hardened underneath, and rock the seal back-and-forth, if necessary, to allow it to detach from the wax. Don't be disappointed if the seal is not perfect. It should have a rough-hewn look, as though you sealed many things in the course of your day, and in a hurry.
Voila! My "A" in sparkly green wax! (I advise you to reinforce your seal-work with tape, as I imagine modern postal services are bit rougher than delivery by horse and rider.)
I have a friend who collects older seals. I love surprising a new pen pal with this accoutrement. As if letter-writing wasn't already fun enough, now you can seal your correspondence with your monogram, a "heart," a "monk seal," or whatever best suits you!