Remember to shut off the internal battery via the BIOS setting before you mess with the insides of the PC. See https://forums.lenovo.com/t5/ThinkPad-T4...

I opened the PC according to the descriptions I found on these pages (There are way more pages listed for Wi-Fi Antenna replacement but the below are enough)

Remove LCD bezel https://pcsupport.lenovo.com/dk/da/solut...

Remove LCD hinge cap https://pcsupport.lenovo.com/dk/da/solut...

Remove base cover https://pcsupport.lenovo.com/dk/da/solut...