Brick lintels support the brick over an opening. after the mortar sets, the wall and the lintel become a unit. Zen, yin and yang, mang. The header of 2x6s will be needed to support the floor system. The header sits either on top of the block or the wooden stud frame, if you have a stud frame.
To install a lintel right, you have to remove the brick all around the area where you want to install it. 1 or 2 bricks above, 1 or 2 bricks out to the sides. When you lay the brick back up to the level of the header, lay the lintel on and lay the rest of the brick right on it. Many times, a 2x4 cut to fit from the sill to the lintel, will be used to keep the lintel from sagging or twisting from the load until the mortar sets.
You're doing a good thing, do it right and it will be fine.