Clarify usage instructions

README.md

@@ -3,13 +3,15 @@
 Repository for storing performance benchmark results.
 
 ## Generate performance graphs locally
-```
+```sh
+# get benchmark results and processing script
 git clone [email protected]:kokkos/benchmark_monitor.git
 git clone [email protected]:kokkos/kokkos-benchmark-results.git
 cd benchmark_monitor
-
+# create and activate virtual environment
 python3 -m venv env
 source env/bin/activate
+# continue inside a virtual environment
 pip install -r requirements.txt
 python benchmark_monitor.py -d ../benchmark-results -o output
 ```