It does not appear that HPE has implemented the ability to run LeanFT Tests from Lab Management. The best thing to do to get such capability implemented would be to open an enhancement request with HPE.
In the meantime, here are some links that may help with running LeanFT Tests from ALM, I hope they help you:
[How to run LeanFT Tests created in Eclipse from ALM]
[How to run LeanFT Tests created in Visual Studio from ALM]
[How to view LeanFT Test Results in ALM]