Hi, and welcome to the forum. Coal needs all the air coming into the stove to go through the coal bed. Unlike wood, which burns just fine with air added over the top of the fire, a coal fire will just go out unless all the air is being pulled through the coal bed.
Make sure your air vents in the loading doors are closed, and the gaskets or rope seals on the doors and glass [if you have glass in the doors] are in good shape.
Then make sure your chimney is clean, if you just replaced a wood stove, with this new stove, you may have an accumulation of creosote clogging or restricting your chimney.
Leave any hand dampers in the chimney wide open untill you either get a manometer to measure draft or get a lot of expertice with burning coal. You want to maximize your draft for now.
Next is the coal itself, all coal is not equal, like wood, coal is a product of nature, and therefore lots of variations. What company or brand of coal are you burning?? Some coal is very difficult to burn well, some is a dream. Let us know.
You must have the coal covering the entire firebox. Don't allow an open corner or edge. Remember the air will 'sneak' around the fire if it can, starving the rest of the coal bed for needed combustion air. once you have the coal fire established you need to fill the firebox up to the top of the firebricks, the deeper the better. You wil control the heat output with the air control in the ashpan door.
You might want to read this thread, I think it is the same or similar stove to yours: Great burn, no heat, what am I doing wrong?
Hope this helps. Greg L