I.How to use roller to creat  stripes on Wall
Step 1: Using Tape to protect
Use the paint tape around the switch ceiling, windows, doors,or wall edges which you don’t want to be painted before you begin the painting project.

Step 2: Cleaning and smoothing the wall
Use a putty knife or multi tool to fill cracks, holes or surface imperfections before painting Then take a cloth or sponge to wipe down the wall to remove dust. make sure your walls are clean.

Step 3: Do by your hand

Normally ,vertical stripes are recommended in most spaces, since they elongate the room and make ceilings appear higher.
Measure and calculate the total area of the wall  being painted , and determine how many stripes there will be. It’s useful to draw a blueprint of the room’s dimensions and map out the stripes on paper, tweaking the size of the stripes to suit the dimensions so that all stripes will be of equal size.

Step 4: Measure
Using measuring tape, a level, and a pencil, mark the top and bottom lines of where each stripe will go. To make a pencil mark between them along a straight level. (Should be very precise )

Step 5: Tape
Place painter’s blue tape along the pencil line outside the area to be painted. Press firmly so the sides of the tape are flush with the wall or you risk jagged lines.

Step 6: Cut In
Position a straight edge on top of the painter’s tape to keep the straight edge and tape line of up. With an angled brush, paint lines against the border of the straight edge. This ensures that the margin will be clean.

Step 7: Paint
Using a roller if the stripe is thick or a brush if thin, apply color between the taped-off areas using the W technique. Roll on a W pattern, and then fill it in without lifting the roller. Continue in sections until you’re finished.

Step 8: Apply a Second Coat
Allow the paint to dry for about an hour then put on a second coat. Once all stripes have just about dried―several hours at least―remove the tape. If you wait until it’s fully dry, you could peel off paint with the tape.

II.Painting a Room by Six Steps
Step 1
Clean walls. Remove dust, dirt, and grease spots (which can ruin a smooth finish) with water, a little mild dishwashing detergent, and a cellulose sponge. Rinse walls with clean water to remove the soap residue.

Step 2
Tape the trim, window, and doorframes. Be sure to use painter's blue tape, which can be applied up to a week ahead. Remove tape immediately after painting, before the wall dries, so you don't peel off any paint with it.

Step3
Prime the walls. It's a common myth that walls that have been painted many times don't need to be primed. In fact, primer helps maximize the sheen and coverage of paint and gives the finish coat a more uniform appearance.

Step 4
Brush where you can't roll. Brush on paint around trim and in the corners of walls, where your roller can't reach, with a two-inch angled brush. Extend out two to three inches from windows, doors, and moldings.

Step 5
Use the W technique. For efficiency, start in the corner of a wall and roll on a three-by-three-foot W pattern, then fill it in without lifting the roller. Continue in sections until you're finished. Paint one wall at a time.

Step 6
Paint the trim. When the walls are completely dry, tape where the trim meets the wall. Paint the moldings and the door and window frames with a two-inch angled brush.