The place to get all the information you need is here --->
https://forum.xda-developers.com/
Input the make and model of your specific phone
then select ---> Roms, kernals, recoveries and other development
1st install the TWRP (Team Win Recovery Program) for you specific phone. This is usually done using ADB Fastboot from a computer tho there are exceptions for some specific phones to install TWRP with software to your phone without a computer.
2nd download the Rom of you choice for your exact phone and copy it in you phones memory or SD card.
3rd download the GAPP, onto phone memory or SD card, for your phone these are all the google stuff the one you download is by which version of android your new Rom is based on and the amout of google stuff you want. (I recommend you use the nano version as it has the least bloatware and intrusions from google.)
4th boot into TWRP recovery and BACK UP YOUR CURRENT ROM then install the ROM as per the ROM instructions ( some require you to wipe your phone first)
5th then still from TWRP install your chosen GAPPS
6th then you can choose to ROOT your phone for even more control and options. This can usually be done from the newer TWRP program itself without additional app follow the instructions from your choosen
ROM.
It seems confussing at first but is really very simple to do. If you need more help let me know your specific phone and model and I'll help if I can. I've done it dozens of time.
The place to get all the information you need is here ---> https://forum.xda-developers.com/
Input the make and model of your specific phone
then select ---> Roms, kernals, recoveries and other development
1st install the TWRP (Team Win Recovery Program) for you specific phone. This is usually done using ADB Fastboot from a computer tho there are exceptions for some specific phones to install TWRP with software to your phone without a computer.
2nd download the Rom of you choice for your exact phone and copy it in you phones memory or SD card.
3rd download the GAPP, onto phone memory or SD card, for your phone these are all the google stuff the one you download is by which version of android your new Rom is based on and the amout of google stuff you want. (I recommend you use the nano version as it has the least bloatware and intrusions from google.)
4th boot into TWRP recovery and BACK UP YOUR CURRENT ROM then install the ROM as per the ROM instructions ( some require you to wipe your phone first)
5th then still from TWRP install your chosen GAPPS
6th then you can choose to ROOT your phone for even more control and options. This can usually be done from the newer TWRP program itself without additional app follow the instructions from your choosen
ROM.
It seems confussing at first but is really very simple to do. If you need more help let me know your specific phone and model and I'll help if I can. I've done it dozens of time.