Im having a few problems with the find command. IM rather new to linux so it could be very simple sorry to waste your time but all help would be great.

What i want to do is search a directory for files that are more then 500kb this is what i have come up with but it doesnt seem to be working very well.

find /usr/bin -exec {-size +500k};

im not real sure why its not working i think it has something to do with the exec command but i feel i need it from what i have read. If someone could explain it to me what i have done and what i need to do that would be great.

Thanks in advance.

Use simply
You can use -exec if you want to manipulate each result of the find command and pass the results as argument to the specified command.
Silly example:

You don't seem to be doing anything with the -exec option, so I don't understand why you think you need it.

The {} curly braces are probably being eaten by Bash because it uses them in a few different contexts. Again, I don't understand why you think you need them.

The following command will find all files in the current directory, and recurse all subdirectories, greater than 9K in size.

This command will do the same, but will not recurse subdirectories.

This last command will show a long style listing of all selected files sorted by size.

http://www.linuxcommand.org/man_pages/find1.html