First, create an elevation deliverable (contours, DEM, DSM, etc.) by following this tutorial.
Once you have an elevation layer in your Layer menu, click on the download button to open the Download Layer menu.
Update all of settings in this menu that are relevant to your project needs:
- Format: specifics the file format of the layer download
- Coordinate system: a drop-down menu that allows you to pick from a few popular options, or select custom to input your own.
- Vertical units: units of the elevation parameter in the data set.
- Horizontal units: units of the horizontal coordinates in the data set.
IMPORTANT: To ensure that your data download matches your desired coordinate system, select the Custom coordinate system and then enter the EPSG code from Step 4.