First, identify the type of dog crate you have before trying to put it together. Folding steel dog crates typically assemble by unfolding the dog crate and snapping the panels into place. Drop pin steel dog crates assemble using long drop pins to hold panels together. Plastic dog crates usually use screws or wing nuts to join the top and bottom halves together.
Folding steel dog crates are the easiest type to assemble. With the crate in the upright, unfolded position, lift the front and rear panels into place. These crates usually have metal snaps or hooks located along the top of the front and rear panels. Click these snaps or hooks onto the top panel, and then complete the assembly by sliding the liner into the crate.
Assemble a drop pin crate by lifting the front, back and side panels into place. Assembling this type of crate is much easier if you have an assistant hold the panels in place while you slide the drop pins into the vertical series of loops at each of the crate's four corners. After installing each drop pin, snap the crate's top into place and slide in the liner.
Assemble a plastic dog crate by fitting the top and bottom halves of the crate into position. Make sure that the crate's door is in its fittings before screwing the top and bottom halves of the crate together.