why cant i empty my trash it says i don't have permission to access some of these items

Right click on the hard drive icon and select Get Info. (If there is no right click on your mouse, click once then type command + i - two keys together).

This is the bottom part of the pane that comes up:

1. Click on the padlock and authenticate with your password.

2. Look at your name and make sure it says "Read & Write. If it does not, change it by clicking on whatever is there.

3. Click on the gear, and select "apply to enclosed items".

This will take some time. When it is done close this pane.