Rehydrate Your Starter

Couple things to keep in mind: always combine the starter with the water first, stir well then add the flour. Also use filtered drinking water, tap water contains chemicals that can kill your starter.

1. Day 1 – In the morning, combine 10g dried sourdough starter in a 8-16oz glass jar. Add 25g of lukewarm filtered water. Stir well. Loosely cover with a lid and store on your counter for 6-8 hours. In the evening, add 25g flour to the water mixture. Stir well. Loosely cover with a lid and store on your counter overnight.
2. Day 2 – In the morning, take out 10g of your starter mixture and add it to a clean 8-16oz jar. Next, combine the 10g of starter with 25g water, then stir in 25g of flour. Loosely cover with a lid and store it on your counter for 24 hours. 
3. Day 3 – In the morning, the mixture will probably look smooth and thin in texture with a few bubbles. Take out 20 grams of your starter mixture and add it to a clean 16oz glass jar. Next, combine it with 40g of water, stir in 40g of flour. Loosely cover with a lid and store it on your counter for 24 hours. 
4. Day 4– In the morning, there should be bubbles. Test your starter to see if it’s ready to bake with, use a clean spoon and take a little amount of your starter and drop it in a cup or bowl with cold water. If it floats, you're good to refresh it to a dry starter or use it to bake with. If it sinks, repeat day 3 steps- take out 20 grams of your starter mixture and add it to a clean jar. Next, combine it with 40g of water then stir in 40g of flour. Loosely cover with a lid and store at room temperature. Test it again in the evening.
5. Read here how to refresh and get your starter ready to bake with!