These achievements require that you use a cumulative total of 50 and 200 power-ups across all of your games. Power-ups can only obtained from opening luggage. To use a power-up in a match, the green power bar on the right must be full. This bar naturally fills slowly over time but will also jump up a tad each time you daub a number that has been called. Once the bar is full, you can tap the blinking icon at the top of the bar to use the specified power-up.
There is no reason to save power-ups for later games. Use them as you get them. However, be smart about it. See the "General Tips" sections at the end of the Roadmap for more information on power-ups.