In Libreoffice Writer, I am trying to make all my numbered headings in the following form:

1. First title

     1.1 Subtitle

     1.2 Subtitle

2. Second title

     2.1 Subtitle

     2.2 Subtitle

         2.2.1 Subsubtitle

I tried playing around with Tools > Outline Numbering, but the best I can only get one of the following:

1. First title

     1.1 Subtitle

     1.2 Subtitle

2. Second title

     1.3 Subtitle

     1.4 Subtitle

Or

1. First title

     1.1 Subtitle

     1.2 Subtitle

2. Second title

     1.2 Subtitle

     1.3 Subtitle

Is there any way for me to put the subheading's numbering as a function of the numbering of the heading above, like in the example on the top?

I am running a .docx file in LibreOffice 4.0.3.3.

Edit: I edited this question as per suggestions in the comments.

Problem solved:

It seems like the big problem was the following. All the headings in the original file had a correct format (i.e. Heading 1, Heading 2, etc). However, they had not been correctly converted to the "corresponding" Heading 1, Heading 2, etc that Libreoffice uses (Thanks @gertvdijk). Thus, followin the steps in the accepted answer gets the job done.

Thanks!