A picture on a screen and thread on a garment are nine steps apart. None of them is hard, and most failed first stitchouts come from skipping a step rather than from getting one wrong. This is the whole journey in order, with the detailed guide for each step linked where you need it.

Embroidery has no tones, only thread. Flat colours and clear edges sew well; gradients, soft shadows, photographs and hairlines do not. Simplify before you digitize: merge near-identical shades, because every colour is a thread change, and thicken or drop any line thinner than about 1.5 mm. The logo guide goes through this in detail, and small text has its own limits.
Digitize at the size you will sew. Scaling a finished design changes its density and how much it pulls, so a design stretched from 60 to 100 mm sews thin. Then set the hoop you will actually use, from the Hoop menu. The hoop on the canvas is your guide to what fits: keep the design inside it with a little margin, since the needle cannot reach the frame.
There are two routes, and most designs use both.
Either way, each shape gets a stitch type. Satin for anything long and narrow, fill for areas wider than about 12 mm, run for fine detail. Satin or fill covers where the changeover is.
The same artwork needs different numbers on a polo shirt, a towel and a canvas bag. Density decides how heavy the stitching is, underlay holds the fabric still underneath it, and pull compensation makes up for shapes sewing narrower than they were drawn. If in doubt, go looser: too dense causes more failures than too light.
Press Export and choose the format for your machine. All ten formats are on the free plan.
The rest are in file formats. Keep your editable design as well: File, Save .stc. A machine file is only a list of needle points. It has forgotten which shape was a satin and what its density was, so it is the wrong thing to come back and edit.
Most machines read a USB stick. Copy the exported file onto it, plug it in, and choose the design on the machine's screen. If the file does not appear, the usual reasons are a stick that is too large or not formatted as FAT32, a file name the machine finds too long, or a folder it does not look in. The machine's manual says which.
Hoop the fabric taut but not stretched: stretched fabric relaxes when it comes out of the hoop and the design puckers with it. Choose the stabiliser for the fabric, not for the design. Then sew a test on a scrap of the same fabric with the same stabiliser. It is the step people skip, and the one that saves the garment.
What to look for in the test:
Change one setting at a time, so you know what fixed it. Open the .stc, make the change, export again, and sew. When the test is right, the garment will be too.
It follows the brand. Brother and Baby Lock read PES, Janome reads JEF, Tajima and most commercial machines read DST, Bernina and Melco read EXP, Pfaff and Husqvarna Viking read VP3. If you are not sure, the machine's manual lists it. Exporting the wrong one does no harm: the machine simply will not show the file.
Most machines read a USB stick: copy the exported file onto it, plug it in, and choose the design on the machine's screen. Some older machines want a small stick formatted as FAT32, a short file name, or a particular folder, so when a file does not appear those are the first things to check in the manual.
Thread pulls fabric in along the direction of the stitches and pushes it out across them, so shapes sew a little narrower one way and wider the other. The fabric, the stabiliser and the hooping decide by how much. The preview shows where the needle goes; a test sew on the real fabric shows what the fabric does about it.