Given the Turing machines M1 and M2, is L (M1) = L (M2)? is decidable?
As you suggested, think how to reduce from the halting problem $Halt_{TM} = \{ \langle M, w\rangle: \text{$M$ halts on $w$} \}$. On input $\langle M, w\rangle$, the reduction should output a pair of TMs $\langle K_1, K_2\rangle$; such that $M$ halts on $w$ iff $L(K_1) = L(K_2)$.
This is somehow a basic reduction that can be done by standard tricks, so it would be a nice exercise to solve it alone. Here is a hint.
Hint: you can simplify things by fixing one of the machines $K_1$ or $K_2$ to be a constant machine that recognizes some fixed language. Then, think how to define the other machine depending on the reduction's input $\langle M, w\rangle$.