To "be employed" means that you have a job. To express what your job is in a formal way, use the phrase "employed as ___":

Sylvia is employed as a financial analyst at a major bank.

I was previously employed as a digital marketing manager.

And to express where you work, use "at ___". You can say the type of company that you work for, or the nameof the company:

He is employed as an engineer at Cisco.

Remember that this is quite a formal way to express your job title. In normal conversation, just say:

Sylvia is a financial analyst at a bank.