It isn't recommended to edit the configuration files directly. If you are relatively new to F5, avoid direct editing of the files.
If you still want to proceed editing the configuration files directly, you would need to execute the following after editing the file:
tmsh load sys config
Its best to use the following command to add the new pool with new details by copying the old pool details:
load sys config from-terminal merge
Copy and paste the configuration through F5 cli terminal
user@(xxx)(cfg-sync In Sync)(/S1-green-P:Active)(/partition)(tmos)# load sys config from-terminal merge
Enter pool configuration( which you have already prepared for new pool or use right click for paste option to paste the pool config)
Press CTRL-D to submit or CTRL-C to cancel.