Ok, this would appear to be homework, so I won't give the full answer; I'll get you started.
First thing to do (with this attack approach) is to write out the full equations of the system, as in:
$$T_0 = P_0 \oplus K_0$$
$$T_1 = P_1 \boxplus T_0$$
$$T_2 = T_0 \oplus T_1$$
$$T_3 = T_2 \oplus K_1$$
$$C_1 = T_3 \boxplus T_1$$
$$C_0 = T_3 \oplus C_1$$
where you know $P_0, P_1$ (the plaintext), $C_0, C_1$ (the ciphertext), and you don't know $K_0, K_1$ (the keys) or $T_0, T_1, T_2, T_3$ (the internal states of the cipher at various points). And, we'll assume that we have a single plaintext/ciphertext pair (that will turn out to be sufficient against this cipher).
Where to do go from here? Well, the first obvious step is to notice the last relation $C_0 = T_3 \oplus C_1$; we know $C_0, C_1$, and so we can deduce the value $T_3 = C_0 \oplus C_1$. Then, we notice the relation $C_1 = T_3 \boxplus T_1$, we know $C_1$ and $T_3$, and so we can deduce the value $T_1 = C_1 \boxminus T_3 = C_1 \boxminus (C_0 \oplus C_1)$. Where do we go next?
Now, this approach takes apart this two round cipher quite nicely; however it doesn't scale very well; adding a third round to this toy cipher will break the relations this depends on. On the other hand, I suppose it might be a start in learning how to think about how to attack a cipher, although you will need to find other ways to attack less trivial ciphers. fgrieu's suggestion about looking at the lower-order bits first is a more general approach that'll work in cases where this won't.