First Step for Installing Rom 

1. Download and install QPST 2.7.422 with QFIL
2. Download and install Qualcomm USB Drivers.

How To Flash ROM Lenovo Vibe P1 

1. Download and install QPST 2.7.422 with QFIL and Qualcomm USB Drivers.
2. Turn off the phone. Hold Vol+ button and plug-in USB Cable. Phone will vibrate one time, screen wil be black. This is DownloadMode.
3. There should be device called in device management:
4. Qualcomm HS-USB QDLoader 9008 (COMXX)
5. In any other case u have to install drivers manually.Run QFIL.
6. Click Browse… in Programmer Path and choose prog_emmc_firehose_8916.mbnLoad XML in Download Section:

1. First select RawProgram File: rawprogram0.xml
2. then Select Patch File: patch0.xml
3. Check all inputs is correct and click Download under Load XML button and wait about 5 to 10 minutes:
4. After flashing process starts and might take up to 5-10 minutes. So keep patience and wait
5. See detailed Instruction Qualcomm flashing  QPST tool with images