Should I activate VPN on my iPad and iPhone? If yes can you please tell me how to do this?

VPN would add additional security if you intend to access highly secured sites such as banking while you are out and about using public WiFi hot spots (from home it is probably overkill). However, unless you already have access to one, such as through an employers as Phil suggests, this would be a service you would need to pay for. There are couple of free ones available, but personally I wouldn't touch them with a 10 foot pole.

VPN stands for Virtual Private Network. Whether you should or not depends entirely on your situation.

Do you need to connect to a VPN?

A VPN is usally provided by a corporate Office or other service for a specific purpose. Only you know if you need to activate it. Your Office IT department would tell you if it is required to access Office resources, and they would give you the settings to use to configure the VPN. Its not something you activate just because you want to.

You're welcome