As an interpreter or translator
Interpreting can be defined as converting spoken statements from one language to another using simultaneous or consecutive interpreting.
A translator converts written material from one language into another.
How successful you will be in developing a career will depend on the market forces in the interpreting and translation business in your language, your experience, your qualifications, your network of contacts and your ability to market your services. Where you live and how far you are prepared to travel are also factors in face-to-face interpreting.
The Chartered Institute of Linguists (CIOL) provides various interpreting and translation workshops (link) and links to other partners offering continuing professional development courses and webinars.
If you wish to focus your career in translation you may wish to consider obtaining a Diploma in Translation (DipTrans) qualification, a post-graduate qualification at Masters level (link), or a Diploma in Legal Interpreting run by Middlesex University (link).
You may also wish to consider a Masters degree in Interpreting and/or Translation. Many universities run courses leading to these qualifications.
The National Register for Public Sector Interpreters (NRPSI) maintains a register for qualified public sector interpreters searchable by interpreters’ clients; see here the criteria to become a member.
Some course providers: