Add instructions for tests

README.md

@@ -17,8 +17,15 @@ Testing is done via the open-source framework [zemu](https://github.com/Zondax/z
 ## Running tests
 
 First [install yarn](https://classic.yarnpkg.com/en/docs/install/#debian-stable).
+Open `tests/build_local_test_elfs.sh` and add your BOLOS SDKs path to `NANOS_SDK` and `NANOX_SDK`.
+This helper script will build the applications required by the test suite and move them at the right place.
+```
+cd test
+./build_local_test_elfs.sh
+```
 Then you can install the project by simply running:
 ```
+cd ..
 make test
 ```
 This will run `make install_tests` and `make run_tests`