sudo openvpn --config path/to/location.ovpn

:~$ sudo openvpn --config ~/Desktop/ra4wvpn-nl-amsterdam-udp-1194.ovpn
Fri Sep  1 13:45:15 2017 OpenVPN 2.3.10 x86_64-pc-linux-gnu [SSL
(OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Jun 22 2017
Fri Sep  1 13:45:15 2017 library versions: OpenSSL 1.0.2g  1 Mar 2016,
LZO 2.08
Enter Auth Username: ******
Enter Auth Password: **********
Fri Sep  1 13:45:26 2017 WARNING: No server certificate verification
method has been enabled.  See http://openvpn.net/howto.html#mitm for
more info.
Fri Sep  1 13:45:26 2017 Control Channel Authentication: tls-auth
using INLINE static key file
Fri Sep  1 13:45:26 2017 Outgoing Control Channel Authentication:
Using 160 bit message hash 'SHA1' for HMAC authentication
Fri Sep  1 13:45:26 2017 Incoming Control Channel Authentication:
Using 160 bit message hash 'SHA1' for HMAC authentication
Fri Sep  1 13:45:26 2017 Socket Buffers: R=[212992->212992] S=[212992-
>212992]
Fri Sep  1 13:45:26 2017 UDPv4 link local: [undef]
Fri Sep  1 13:45:26 2017 UDPv4 link remote:
[AF_INET]154.59.112.130:1194
Fri Sep  1 13:45:26 2017 TLS: Initial packet from
[AF_INET]154.59.112.130:1194, sid=9c75530e 3e238e30
Fri Sep  1 13:45:26 2017 WARNING: this configuration may cache
passwords in memory -- use the auth-nocache option to prevent this
Fri Sep  1 13:45:26 2017 VERIFY OK: depth=1, CN=RA4WVPN
Fri Sep  1 13:45:26 2017 VERIFY OK: depth=0, CN=RA4WVPN
Fri Sep  1 13:45:26 2017 Data Channel Encrypt: Cipher 'AES-128-CBC'
initialized with 128 bit key
Fri Sep  1 13:45:26 2017 Data Channel Encrypt: Using 160 bit message
hash 'SHA1' for HMAC authentication
Fri Sep  1 13:45:26 2017 Data Channel Decrypt: Cipher 'AES-128-CBC'
initialized with 128 bit key
Fri Sep  1 13:45:26 2017 Data Channel Decrypt: Using 160 bit message
hash 'SHA1' for HMAC authentication
Fri Sep  1 13:45:26 2017 Control Channel: TLSv1.2, cipher TLSv1/SSLv3
ECDHE-RSA-AES256-GCM-SHA384, 2048 bit RSA
Fri Sep  1 13:45:26 2017 [RA4WVPN] Peer Connection Initiated with
[AF_INET]154.59.112.130:1194
Fri Sep  1 13:45:28 2017 SENT CONTROL [RA4WVPN]: 'PUSH_REQUEST'
(status=1)
Fri Sep  1 13:45:28 2017 AUTH: Received control message: AUTH_FAILED
Fri Sep  1 13:45:28 2017 SIGTERM[soft,auth-failure] received, process
exiting