I've managed to find all of the subgroups of D14 (6 of order 7, 7 of order 2 and 1 of order 1) but I'm really struggling to put this into a lattice as I've never done it for dihedral groups before, only for symmetric groups. How do I find which of my subgroups are subgroups of the other subgroups? It's very easy with symmetric groups but I think I'm missing something here. Thanks in advance.
Edit: by D14 I'm using D2n notation so in this case the shape in question is a heptagon.