Yes you can.
You can purchase a tournament ticket from the rewards store and use that ticket to enter a tournament.
Some examples are
21,500 stars coins buys a $215 tournament ticket. You can then use that ticket to enter the Sunday Million or some other $215 buy-in tournament.
1,100 stars coins buys a $11 tournament ticket. You can use that ticket to enter the Sunday Storm or some other $11 buy-in tournament.
110 stars coins buys a $1.10 tournament ticket. You can use that ticket to enter the Big $1.10 or some other $1.10 buy-in tournament.
Check out the "Online Tickets" in the "Rewards Store" for further information. There are options to use your stars coins to purchase tournament tickets from 25 to 21,500 stars coins.
Hope this helps and good luck.