Which tetrahedral mesh generator recommend you to study finite element method?
I tried to use TetGen. It works well but I can not install tetview to see the meshes because I have a 64bit computer.
I'm need to work with P2 elements in each tetrahedrom.
The most well-known alternative for TetGen is Netgen. Another approach would be to use another software, e.g. Geomview, to visualize the meshes generated by TetGen.
The usage of $\mathbb{P}_2$-basis doesn't in fact set any additional constraints on the mesher unless you're interested in curved boundary elements which are supported at least by Netgen.