After searching in the software manager for a vpn I discovered that "openvpn" was already installed. Does that mean it is automatically working or do I have to configure it? I couldn't find the software in the application list.

What distro are you using? You will have to configure.

I use Manjaro but I'd rather have taken the time to install Arch

You need to configure it. Manjaro doesn't know which parameters you want for your VPN tunnel. You also need to create certificates.

Many resources are available. For example, installation on a Raspberry Pi: https://raspberrytips.com/install-openvpn-raspberry-pi/. Or documentation at the openvpn web site https://community.openvpn.net/openvpn/wiki/HOWTO. I am sure Archwiki has a page as well.

To activate openvpn on a Linux distro you will need to subscribe to a PAID vpn provider.

You will then have to be careful about which vpn provider you choose.

Wireguard is said to be better than OpenVPN and IPsec.

You're telling me Manjaro has free vpn without a paid service provider?

Well, I run an OpenVPN server on my home server (Ubuntu in this case) so that I can tunnel in from outside. I don't pay anybody anything.

I do have a normal internet connection that I pay for.

Not true. If you have access to the machines at both ends of the tunnel you can set it up as a private vpn. I do so for admin on a PC for a friend who lives ~75 miles from me.

Read this. It may help you with your answer.

https://torrentfreak.com/best-vpn-anonymous-no-logging/

Its not the be all and end all, but its a good start on choosing a VPN provider.

Your choice will probably include what you do online, how much you want to obfuscate what you do, how resilient to court orders you want your provider to be, whether they store your information, etc. So if all you do is use Facebook and Instagram and want to have the VPN on your computer and phone, then any provider will probably do. If you are a pen tester or do bug bounties, you may want something a little more secure.

https://wiki.archlinux.org/index.php/OpenVPN
https://aur.archlinux.org/packages/expressvpn/
https://www.expressvpn.com/support/