org-latex-packages-alist

org-latex-packages-alist is a variable defined in `org.el'.
Its value is

nil

Documentation:
Alist of packages to be inserted in every LaTeX header.

These will be inserted after `org-latex-default-packages-alist'.
Each element is either a cell or a string.

A cell is of the format:

("options" "package" SNIPPET-FLAG)

SNIPPET-FLAG, when non-nil, indicates that this package is also
needed when turning LaTeX snippets into images for inclusion into
non-LaTeX output.

A string will be inserted as-is in the header of the document.

Make sure that you only list packages here which:

- you want in every file;
- do not conflict with the setup in `org-format-latex-header';
- do not conflict with the default packages in
`org-latex-default-packages-alist'.

You can customize this variable.