If you're using alcohol ink to tint the liquid clay, you may want to do that first. Put a drop or two of the ink on top of the liquid clay and allow the alcohol to evaporate before mixing the color into the clay with a toothpick or needle tool. Apply the ink now and mix it in later on.

This "evaporation-wait" may not be neccessary, but it is generally recommended as an extra precaution to prevent unwanted bubbling in the liquid clay.

A little ink goes a long way, so use it sparingly. You can always add more ink later, if you want a darker color. If you accidentally add too much, you can lighten the color by adding more liquid clay. You can also mix custom colors by combining one or more colors of ink.