Equational Logic- L-Structures

Equational Logic- L-Structures

L is the language ${+,*, -, <,0, 1}$. I need help showing that for each $m
\in \mathbb(Z)$ there is an atomic $L$-formula $F_{m}(x)$, having $x$ as
its only variable, that defines the one-element subsets ${m}$ of
$\mathbb{Z}$ i.e. ${a \in \mathbb{Z}: F_{m}(a)}$ is true = ${m}$
I know that an atomic formula is with no connectors and a L-formula is a
pair $(A,I)$ where $I$ is an interpretation of $A$ on $L$. I'm confused
why this formula $F_{m). Not sure where to go from here.
Then I can use that proof to show that for each finite subset $Y=
{m_1,...,m_k}$ of $\mathbb{Z}$ there is an $L$ formuala $F_{Y}(x)$ that
defines $Y$, i.e. $F_{Y}(a)$ if true iff $a \in Y$ i think. I'm just stuck
on how to go about it.