I want to buy an iMac online. I'm from Ecuador

Welcome to Apple Support Communities

As there's no Apple Online Store in Ecuador, you can't buy the iMac from there, as you need to purchase it from your country's Apple Online Store.

Instead, you have to look for another website that sells iMacs, like Amazon. Probably Amazon can send you an iMac to your country, and the only thing you have to make sure is that it comes with a Western Spanish keyboard, which is the one you probably want. In that case, visit the Spanish Amazon site > http://www.amazon.es

There are also other sites to buy it

Authorized Apple dealers are not allowed to ship outside of their home country, so the only way someone could order through Amazon and get shipment to Ecuador would be by using an Amazon affiliate or other dealer that is not an authorized Apple reseller.

Regards.

Mitre, you can look for authorized Apple dealers in Ecuador here:

https://locate.apple.com/ec/es/

If there are none where you live, you can call dealers in other cities in Ecuador and ask if they'll accept a phone order and ship the iMac to you.

Regards.