This article explains how to switch Gmail accounts in any web browser. First, you need to know how to link your Gmail accounts.
How to Switch Between Multiple Gmail Accounts in One Browser
You will first need to link your Gmail accounts in order to switch between them and access them simultaneously:
In the top right corner of Gmail, select your profile icon and choose Add Another Account from the pop-up menu.
Enter the second Gmail address you want to add as a linked account and select Next.
