How do I attach the fans to the tent?

You just need one good fan that can pull through ducting like the one pictured above. Have the fan pushing air out (or pulling it out) of the tent. This will create negative pressure which will automatically suck fresh air in - no need for a second fan. The fan you purchased can move a bit of air but it has no capacity at pushing it through ducting. If you take the fan you have and put it directly into one of the upper sleeves of your tent with no other ducting it might move enough air to help cool the tent a bit.