Tarosuma, put it in a clean glass jar feed it with equal parts of filtered water and bread flour. Leave it at room temperature until it forms bubbles on top, then feed it again and leave on kitchen bench for a couple of hours, then into fridge. Depending on size of 'lump'. about 1/2 cup of each water and flour.
Filtered water is very important as chlorine will kill it.
When you want to use it, remove from fridge and feed again. It will take 7 hours to come to room temp and start working. After this you can use it. when you remove some starter, feed it again and put in fridge.
There are several recipes for using it on the Forum, also on my blog. Good luck and ask for help if needed.
