You can access money in your pension if you're over 55 years old (57 after 2028). This is known as the normal minimum pension age and it's set by the UK government. 

In terms of what you can do before then, it's either:

1. Let your pension sit tight where it is or
2. Move it over to another provider

It's worth noting there are some special cases where you might be able to access your pension earlier, such as if you have a terminal illness. In these situations, the trustees will have a look at everything on a case-by-case basis. Want to know more? Check this out.