There is not a built in spell check or grammar feature in Microsoft Excel, but there are a few ways to workaround this.
One option is to copy and paste your text into another program that does have spell check and grammar features, such as Microsoft Word, and then copy and paste the corrected text back into Excel.
Another option is to use an online spell checker and grammar checker, such as Grammarly (https://www.grammarly.com/). You can either copy and paste your text into the online tool, or install the Grammarly plugin for Microsoft Office, which will work with Excel (https://www.grammarly.com/office-plugin).