First you will need to create a forum gold security password. To do this click on Forum Gold at the top of your forum page. Once there you will click "Edit Security Settings". On the next page click the "Set New Gold Security Password" link at the bottom.
Next, you need to click the gold icon , which will open a small popup box with a form. The first field is the "Amount" you wish to send. The second is "Comment", which can be something like "Thanks for the runes" or something similar. The third line is to type in your "Gold Password".