If you sold your item then you should mark it as SOLD by editing your post.

• Go to your ad
• Click on "Edit"
• Find "Listing Status"
• choose "SOLD"
• Go to bottom of page
• Click "SAVE"
  

If you've decided to remove the ad, you have the option to delete it.

• Go to your ad
• Click on "Edit"
• Go to bottom of page
• Click on "Delete"