Right the first one goes like this lol

1) paint the entire nail black and allow to dry
2) take a piece of sponge and dip in white paint dab onto left bottom corner of nail
3) Paint a x shape and then sweep a line through it to create a star shape
4) Take a dotting tool and dot the end of each star shape to make a snowflake
5) Do a few more dots with smaller end of dotting tool to make stars
6) Bottom left draw stocking shape with black paint and fill in all white allow to dry and add red stripes
7) Taking a fine nail art brush sweep downwards to create fir tree shape in green once dry take white and sweep randomly to create a snow effect
8) You can now add a star to the top of your tree and paint on shiny balls, bows etc
9) Dip your fingertip into white paint and press onto nail to create snowmans body dip again using a smaller finger to make the head allow to dry
10) Take your small dotter and add eyes, paint on a hat if you wish and add some arms with small brush.

Picasso eat your heart out lol