First calculate the bond price. Then divide annual coupon rate by the price.
Bond Price = ∑i=1n C/(1+r)n + F/(1+r)n Or use any online calc or Excel
https://www.omnicalculator.com/finance/bond-price
Price = 130.15
Current yield = 9.5/130.15 = 7.3%
You can buy Treasuries through a normal brokerage account. Check fees, but at the brokerage that I use there is no cost as long as I let them mature.
You might want to read this: The Bond Book