Many questions will be answered when

Readng this thread.
http://www.rcuniverse.com/forum/m_50..._4/key_/tm.htm

then read this thread about Walkera 22E
http://www.rcuniverse.com/forum/m_3722641/tm.htm
which the Eagle 50 is a clone as are the parts.
When ordering parts double check pictures and actual parts concerning batteries and motors.

But for your immediate answer, many of us cut the rubber rings that are holding the battery,
turn the battery sideways, supported by new rubber bands on the little hooks on the side of the chassis.
Push the battery forward and use the "trim" on the transmitter.
Some people put weight in the nose. Some people switch the battery and the receiver placement.