1. Install TWRP: You must flash the custom recovery using the Odin tool on your PC. You will put the tablet into "Download Mode" (Power + Volume Down + Home) and flash the TWRP .tar file via the AP slot in Odin.
2. Boot into Recovery: Once TWRP is flashed, reboot the tablet immediately into TWRP (Power + Volume Up + Home).
3. Wipe Data: In TWRP, go to "Wipe" and swipe to "Factory Reset." It is highly recommended to format the Data partition as well.
4. Install ROM: Go to "Install," locate your Custom ROM .zip file on your SD card or internal storage, and swipe to flash.
5. Install GApps: If the ROM does not come with the Play Store, you must flash a GApps package immediately after the ROM.
6. Reboot: Go back to the main menu and select "Reboot System."

Conclusion

Where to Find ROMs

• XDA Forums: Samsung Galaxy Tab A (2016) – SM-T280/T285 section
• Telegram Groups: Search "SM-T285 custom ROM"
• 4PDA (Russian forum): Active community for Spreadtrum devices