Hello,
You could either share the Accounts across all companies, or if you foresee that they may differ between the companies in the future, it is best to import the accounts in the new company. Please follow these steps:
1. Log on your existing (old) company
2. Module Integration >> Routines >> Exports >> System Data
3. Tick "Accounts" >> click "Run" and point to where you would like to save the output file.
4. Log on your new company
5. Module System >> Routines >> Imports >> Manual file search
6. Point to the file that you created in step 3.

This will import the Accounts, please make sure they have been created in module System >> Registers >> Accounts.