All API requests are required to be authenticated via an oAuth 2 access token. It's easy to request a token via the command line to get a feel for how things work:
curl -i https://api.layervault.com/oauth/token \
-F grant_type="password" \
-F username="<your layervault username>" \
-F password="<your layervault password>" \
-F client_id="<client_id_goes_here>" \
-F client_secret="<client_secret_goes_here>"
Which will return an Access token response like this one:
{
"access_token":"aec9c670cf5e673bfedf83d055d2a2e0e5f37e52d3b41cffcf7874f73a7458bf",
"token_type":"bearer",
"expires_in":7200,
"refresh_token":"afe9c670cf5e673bfedf83d055d2a2e0e5f37e52d3b41cffcf7874f73a7458bf",
"scope":"user"
}