We have strongly chlorinated tap water water in the czech republic. The first step is to pour water into a PET bottle the night before the dive.
1) Put the sock on the EMWL: Rubber band on flat port. Rubber band on heel. Leave the EMWL vent holes open (bubble ring released). Put the sock on the EMWL. Rubber band on the objective lens.
2) Fill the sock with clean water: Fill the sock with clean water. Release all bubbles by moving the sock at places where are the EMWL connections (bubble rings are released all the time). Add more water to fill the sock up to the maximum (no air in the sock).
3) Close the cap. Now you can test that everything is OK. EMWL will focus above the surface with this "adjustment".
If you have well-tightened rubber bands, it holds clean water very well. In my case, I have half an hour filled EMWL on shore. And then the water stays inside the whole three-hour freedive session.
The first installation takes a little longer and I recommend trying it for the fisrt time in peace at home. If you know what and how, then the installation at the dive site will not take you more than 5 minutes.