Free Member Wars

I am a free member on Simcountry.

I read something about attacking a C3 country, looting it's workers and goods, dropping it, and then attacking another one, looting it, dropping it, ect.

So I conquered a C3 country, looted it entirely, and then dropped it. I tried to declare war on a second one, and it wouldn't let me, saying that free members can only extend their empire to 2 nations. This is confusing to me, seeing as I only had one country at the moment.

Are free members only allowed to declare war once, even if they have only one country, or am I doing something wrong here?

Follow up question: If indeed free members can only declare war once, how do I upgrade my membership? I cannot find the place to do that, or the price I have to pay. What is the price of that, and where do I do it?

Free members can conquer a country and see how it works.
to really fight wars, purchase all weapons and build a strong army, you need to become a full member.

There is an option on the left side menu, called

Membership.