You don't - That's what it's for. The idea is that you put any frequently
used bits of code in there, such as macros that you might want on a regular
basis, but are not necessarily specific to any workbook. It opens up hidden
(normally), and then any code in it is available to you whilst in any other
workbook.
If you really really want to stop it opening, then just move it into a
different folder but you really are defeating the purpose of the file.
If it's opening and is visible then just use Window / Hide and it will
disappear, then choose to save changes to personal macro workbook when
prompted after closing Excel.
