If you have just written Raspberry Pi OS to your microSD card in the SD card adapter, first you need to eject your SD card adapter first.
Eject microSD
Then you can eject your microSD card from your SD card adapter.
Insert the microSD card to the slot
Insert the microSD card to the microSD card slot in your Raspberry Pi.
Please make sure you inserted the microSD card to the end of the slot.
Connect your PC and your Raspberry Pi using an Ethernet cable
For a direct-connection, you can connect your PC and your Raspberry Pi using an Ethernet cable.
Connect power to Raspberry Pi
Then you can connect power to your Raspberry Pi. In most cases, we use AC adapter to supply power.
On connecting the power, the system will automatically boot. You need to follow the next steps before you can shut down your Raspberry Pi. Please refrain from simply disconnect power from Raspberry Pi; doing so may damage or even break your Raspberry Pi.
Insert microSD card to Raspberry Pi
Eject SD card adapter, if you used it
If you have just written Raspberry Pi OS to your microSD card in the SD card adapter, first you need to eject your SD card adapter first.
Eject microSD
Then you can eject your microSD card from your SD card adapter.
Insert the microSD card to the slot
Insert the microSD card to the microSD card slot in your Raspberry Pi.
Please make sure you inserted the microSD card to the end of the slot.
Connect your PC and your Raspberry Pi using an Ethernet cable
For a direct-connection, you can connect your PC and your Raspberry Pi using an Ethernet cable.
Connect power to Raspberry Pi
Then you can connect power to your Raspberry Pi. In most cases, we use AC adapter to supply power.
On connecting the power, the system will automatically boot. You need to follow the next steps before you can shut down your Raspberry Pi. Please refrain from simply disconnect power from Raspberry Pi; doing so may damage or even break your Raspberry Pi.