In order to import a flight plan from Simbrief into the 'Modern' FMC, you will need to follow the guide below:
1. On the FMC, press IDX to open the INDEX page and go to PAGE 2.
2. Click to open MOD SET.
3. Enter your PILOT ID in the scratchpad (should be a 5 or 6-digit number).
4. Press the LSK L2 button next to the - - - - - - under SIMBRIEF PILOT ID header - this will turn GREEN if it has been accepted - this is now stored in the simulator and will remain persistent even after simulator restarts (you can skip these initial steps for future imports)
5. Press IDX to open the INDEX page and go to PAGE 2
6. Click to open ROUTE MENU
7. You should see FPLN RECALL (SB) highlighted with your PILOT ID under it in GREEN.
8. Click FPLN RECALL (SB) and your flight plan should import; you will be returned to the FPLN PAGE and will be prompted to hit EXEC to finalize the new flight plan