The simplest thing you can do with a 4017 (decade counter) is clocking it manually at pin 14 applying positive voltage to it. In that case the pin must have a 10KΩ resistor to ground, because the counter can only see a positive pulse edge. Then apply the positive voltage directly to the pin.
The count advances with every clock pulse.
A better way is to use an oscillator circuit which you can make easily using a timer IC (NE555).
Connect the parts as shown in the schematic. With all 10 LEDs connected you've created an LED-chaser.
This circuit counts through ten and recycles to start all over again.
The frequency of the oscillator circuit is variable from 1 to 20Hz. At the highest frequency the LEDs flash in fast sequence similar to the strobe lights along the final approach course of airports.
The two schematics only differ in frequency setting. Potentimeter tap at the left hand side is slowest frequency and taking it to the right hand side frequency is highest.
LED flashing sequence is from right to left (D10 --> D1)
Using a manual reset button you might make an interesting game with your kids, checking reaction time with the most advanced count losing.
Connect an SPDT momentary switch so it connects ground to pin13 when not pressed. Connect the other side to +9V to be routed to pin13 when depressed. The counter will stop and display the latest count steadily. To reset it for the next round you might do the same for pin 15 which resets the circuit to count zero.
If the power supply does not exceed 9V voltage you might use the circuit as it is. At higher supply voltages you must use current limiting resistors for the LEDs.
Boncuk