How to use Salt correctly with MD5

Question

I’m using Apache Commons Codec to encrypt system users' passwords. Ex:

DigestUtils.md5Hex(usuario.getSenha())

The problem is that depending on the password it can be easily broken, so I thought to create a complex String and always add it at the end of each password created

String salt = "3&1cNM!+<c#KtPzx*";
DigestUtils.md5Hex(usuario.getSenha()+salt)

That way all created passwords would have this concatenated string. My question is the following:

• This would really make it difficult to break these passwords?
• What would be the steps of generating this salt dynamically? That functionary?