If you want to do a work placement or internship during your studies you need to make sure you do this in line with your visa conditions. Further information can be found at UKCISA
You can do any work placement during your defined vacation period.
You can do a work placement provided:
If your course does not contain a work placement you could do a placement during your vacation period or for a longer placement of up to 12 months you may be able to convert your degree to a Degree with Employment Experience.
Opting to do an additional placement year could affect your visa, see here. It could mean that you will need to return home to apply for a fresh Tier 4 CAS and visa before you start the placement. If you are considering this option, please check how this will affect your Tier 4 visa with International Student Support
You can get help on your options to find a placement from here.