Let $\displaystyle p$ be a prime such that $\displaystyle p \equiv 1\bmod 4$.

I want to understand how 2 is a square in $\displaystyle {\mathbb{Z}_p}$.

I have already found this link to the proof: -1 and 2 as Quadratic Residues. But I'm having trouble understanding it.

I kinda need this for graph theory actually. I'm studying Paley graphs.

Thanks in advance!