Cannot defeat a guardian with travel symbol

[HoeCristian]

I cannot defeat the guardian who require a travel symbol, it's only asking me to "travel" to the site but i already have an archeologist here. Where do I have to click ?

[BenInJapan]

I assume you're talking about this game, right?
https://boardgamearena.com/6/arnak?table=463566273

I further assume you want to assume your car token from the guardian to pay for travel to defeat the guardian, as you don't have any cards left in hand and not enough money to pay for a plan. I also assume you want to use your idol to get two tablets, as otherwise you don't have the resources to pay, right?

That being said, usually you just need to click on the guardian you want to defeat, and then click on the travel icon you want to use. Did you try to click on the travel icon when asked to "travel" to the site? It usually works, even with travel icons from guardians, I've done it several times. But you probably need to make sure you have all needed resources available before clicking on the guardian (I'm not exactly sure about this though)

Edit: Oh, I forgot, I also assume you want to try to defeat the guardian at your dig site (the one with foot, tablet and arrow), and not the one at the two idol site (with plane and arrow)