The .ovpn file format is an embedded version of the usual 3-4 files openvpn format. It can be very handy when dealing with mobile setups like android or iOS or on some mac applications like Tunnelblick. According to my recent openvpn post you only need to follow this code:

client
remote example.com
comp-lzo yes
dev tun
proto udp
nobind
auth-nocache
script-security 2
persist-key
persist-tun
user nobody
group nogroup

<ca>
-----BEGIN CERTIFICATE-----
# insert content of your ca.crt
-----END CERTIFICATE-----
</ca>

<cert>
Certificate:
 # insert content of your user.crt
-----END CERTIFICATE-----
</cert>

<key>
-----BEGIN PRIVATE KEY-----
# insert content of your user.key
-----END PRIVATE KEY-----
</key>

Remember to transfer that key securely, do NOT send this via unencrypted email to you external device 🙂