Make wood spacers from ½-inch by ½-inch boards, cut to 3-foot lengths with a circular saw or a hand saw. No special type of wood is necessary for the spacers; you'll use them to obtain a rough level on your mortar.
Lay out your brick pattern as you want it to look beside your walkway. Unless you're a professional mason, this is the best way to get the exact pattern you want. You don't have to lay out the entire walkway at once, but lay out enough to complete at least a 3-foot length of walk. You can lay out more as you go.
Cut a section of plywood to the dimension of the width of your walk. For a standard 3-foot residential walkway, you would cut a square of plywood that is 3 feet long and 3 feet wide.
Place one spacer on each side of your sidewalk at the start of your walk. The spacers serve as a rough level, helping you keep the mortar bed even.
Mix mortar as directed on the bag and spread it out on the concrete between the wood spacers, creating a 3-foot "bed" of mortar about ½ inch high over the level of your walkway, using the spacers on each side as rough guides. It need not be perfectly even.
Transfer the bricks, maintaining the same pattern, from beside the walkway to the mortar bed. Do about 3 feet at one time, working from side to side on the walkway.
Set each brick as you place it by pushing it back and forth lightly. The bricks will sink about ¼ inch into the mortar bed, displacing some of the mortar between each brick.
Complete a 3-foot area and then place the plywood square lightly on top of the bricks. Tap lightly over the entire surface of the plywood with a rubber mallet to level the bricks beneath. Remove the plywood and use a trowel to wipe away excess mortar that has seeped out on the edges of the walkway. Repeat with the each 3-foot section of walkway.
Spread fresh mortar over the bricks after the entire brick walkway is complete and the mortar bed is hard. Use the trowel to push the mortar evenly into the spaces between the bricks, wiping excess mortar off the top of the bricks as you go.
Brush away dried mortar from the brick surface with a stiff-bristle brush, when the mortar is completely dry.
Spray off the surface of the bricks and your walkway is ready for foot traffic.