Easier appraoch:
brew install bitcoin
However, as Jonas points out, you should be careful with trusting 3rd party package managers. Specifically, you should verify the SHA1 of the package you're getting from Homebrew matches that of the [official release of Bitcoin](https://bitcoincore.org/bin/) from either GitHub or the Bitcoin Core website.
More reading:
[Is Homebrew safe?](https://apple.stackexchange.com/a/241768)
Example of using GPG to verify a package's signature (in this case the `SHA256SUMS.asc` signature file in https://bitcoincore.org/bin/bitcoin-core-0.15.1/):
