First you will need a digital model of your molecule of interest. There are multiple options to generate a 3D printable protein model. These instructions are written for the popular software ChimeraX. You can download in UCSF ChimeraX.
Find your model on the Protein Data Bank and download in PDB Format (gz). In case you haven’t yet, download and install ChimeraX (Free for private use and academic or research institutes). Start ChimeraX and open the file (File -> Open).