EDTA is not a pH buffer at pH 8.2. It is used to bind up (chelate) metal ions. To dissolve EDTA, which is acidic, you must add base, normally NaOH. If you are starting from EDTA, you will need ~4 equivalents of NaOH, but if you are starting from disodium EDTA you will need only ~2 equivalents.

For the volume and concentration of EDTA you need for your buffer, weigh out the appropriate amount of the solid into a beaker with a magnetic stir bar. Add distilled water, but not the full amount, because you will need to leave room to add concentrated NaOH solution. If you are making a large amount of concentrated EDTA, you may find it convenient to add NaOH pellets.

Set the slurry of EDTA stirring and gradually add the NaOH. Once the EDTA starts to dissolve, begin monitoring the pH. As the pH approaches 8.2, adjust the volume to almost the full volume with distilled water. At this point, you should allow the solution to cool down, because it will be hot and pH is temperature-dependent.

Once the solution is at room temperature, finish the titration, and adjust the volume with water to the final volume.

Or, to save time, buy the premade solution from a chemical supplier.