Blade tension is essential to a good cut on a band saw. Right above the cutting table, where the blade disappears up into the housing, there is a small metal block with a slot that the blade runs through. Some of these will have a round bearing against the back of the blade; others have a nylon guide. This is the blade guide. Release the guide by turning the nut on its side counterclockwise. Allow it to slide down to the top of your material, as it lies on the saw table. Lift it up just enough to give clearance, then tighten it in position. This keeps the blade as straight as possible for smooth cutting.
Band saws come typically equipped with a removable rip fence, similar to a table saw fence. Set this up, then measure the distance from the blade to the fence. Adjust the distance to the thickness you want and lock the fence in place by twisting the lock mechanism clockwise, or flipping the locking cam handle down fully, depending on the saw. Start the saw and run the material to be ripped through the blade, with one edge against the fence. Use a push stick to complete the cut, keeping fingers well clear of the blade.
Mark curves on your material and adjust the blade guide for the thickness of material being cut. Start the saw and run your material through the blade, free hand (without a fence), turning the material to follow the outline you drew. Remember that, unlike a jigsaw, or reciprocating saw, the material must move and not the blade, so focus on positioning the wood so that it feeds through the blade without bending it.
Locate the miter gauge on the front of the saw and the bevel adjustment near it. Turn the adjustment lock counterclockwise to release and tilt the saw table to the desired pitch. Turn the lock back clockwise to fasten the table in place. Fit the rip fence onto the saw and adjust it to the width of piece you want to cut. Start the saw and pass the wood through, keeping one straight edge against the fence. Use a push stick, if needed, to pass narrow pieces between the fence and blade, to protect your fingers.