Building (2) enclosures, both 4x2x2'

[DeesBalls]

Ok, so i cant stop doing lil projects... i am going to be building two enclosures out of melamine, i believe 3/4 ". i found a big sheet that is 4.08 foot wide, by 8.08 ft long... I am going to be cutting that into 3 pieces of 2 foot x 4 foot peices, and then the last peice of 2x4, ill cut in 1/2 and get 2 pieces of 2x2 for the sides... here is a diagram...(attachment)

im just trying to get everything in order, i want to get the sheet starting sooon, i will be making one for my Bearded Dragon 1st, then my BRB. i will have questions along the way..

my 1st is, how would i put in ways to heat? i seen people add ceramic heat emmiters in but how do they get them to work?

any way, hope i have verything straight and everything will work out, also what would you guys suggest for a door/front??