When you download the browser extension from GPEX Wallet's official website, please check your browser's extensions. Depending on the browser you are on, the steps are as follows:
You will see your extensions under this icon. Clicking on it will bring down the dropdown where you can pin your GPEX Wallet extension:
You can find details about your extension in the Manage Extensions section: chrome://extensions/ or by clicking the 3 dots menu on the right next to the extension you would like to manage.