With your plane--yes, you balance the plane empty of fuel. This represents the aft most position of the CG. So, when you fill it up with fuel, the CG moves forward--which is manageable. However, on pusher type planes--and in any case where the fuel tank is located behind the CG, the plane is usually balanced full of fuel--again, representing the aft most point of CG.

To reitereate--with your trainer--empty of fuel, and on the spar would be a great spot to start--especially with such vague instructions!