The weeds are taking advantage of open soil with sunlight.  A broadleaf weed killer should take care of them when applied per container instructions.  Make sure it is for broadleaf weeds and NOT GRASS.  Once weeds are dead, consider top dressing with a mix of good top soil and compost to level the area.  You can then seed the appropriate grass seed.  Again, make sure to follow directions on the package.  You get what you pay for with grass seed so it is worth purchasing good seed rather than a cheap brand which may have inappropriate material.Then water as directed.  New seedlngs dry out quickly.