There are 7 things you need to do when employing staff for the first time.
1/ Decide how much to pay someone - you must pay your employee at least the National Minimum Wage.
2/ Check if someone has the legal right to work in the UK. You may have to do other employment checks as well.
3/ Check if you need to apply for a DBS check (formerly known as a CRB check) if you work in a field that requires one, eg with vulnerable people or security.
4/ Get employment insurance - you need employers’ liability insurance as soon as you become an employer.
5/ Send details of the job (including terms and conditions) in writing to your employee. You need to give your employee a written statement of employment if you’re employing someone for more than 1 month.
6/ Tell HMRC by registering as an employer - you can do this up to 4 weeks before you pay your new staff.
7/ Check if you need to automatically enrol your staff into a workplace pension scheme.
Further information:
https://www.gov.uk/employing-staff