The tank goes in the cavity immediately behind the firewall and will be entirely forward of the wing leading edge.

The Rx can probably go in the area below the front of the wing beneath the steering pushrod and forward of the servos. The battery may also fit there or aft of the servos beneathe the pushrods.
http://www.thundertiger4u.com/pdf/45...rainerMKII.pdf
Look at page 8 of the above manual. Not sure you have this exact plane but it gives you the general idea.