Battery won't show up. Please help

Hi,I am a little bit of a noob but I managed to make everything else working but the battery percentage. I have not installed it yet, I tested everything in the installer. I downloaded the "Laptop Haswell and Broadwell" SSDT-s from the guide: Prebuilt SSDTs | Getting Started With ACPI (dortania.github.io), but I can't see the battery icon in the installer. But I found this: Laptop-DSDT-Patch/battery/battery_Dell-Inspiron-15-7xxx.txt at master · RehabMan/Laptop-DSDT-Patch · GitHub . This is what I need but I don't know where to put these lines in which SSDT. I do not have a DSDT, I don't know if that is a problem. I have tried removing these SSDT-s and placing someone else's. That actually gave me the icon in the installer but the numbers were false.

Laptop: Dell Inspiron 15 7537
CPU: i7-4510u
GPU: HD4400 (+ GT750m)
I have these battery kexts: ACPIBatteryManager.kext, SMCBatteryManager.kext

Thanks in advance,
Borisz