Your next mission is to solve the yellow corners and finish the 1st layer. Here's how.

1. Look for a yellow corner piece in the bottom layer. Something like this. If you find one, skip to step 3.
2. No yellow corners on the bottom? Okay, you have to move an unsolved yellow corner piece from the top layer to the bottom layer. Keeping yellow on top, hold the cube so the unsolved corner is at the front-right, like this, and do any one of the moves in step 4 to move it to the bottom.
3. Turn the bottom layer so the yellow corner piece is under its target position.
4. Now check the corner’s bottom color.

• If the bottom color matches the right side center piece, do these turns:
  
• If the bottom color matches the front center piece, do these turns:
  
• If the bottom color matches the top layer center piece, flip the corner using these turns, then go to step 3.
  

Repeat steps 1 - 4 until all four corners are solved.