Search for them and apply to them. It's very hard to get an internship in security as a first year. You're going to be competing with second and third year students. Make sure your CV is put together nicely.
They aren't going to expect you to really have much (if any) experience so just make sure you fill it with stuff that you've learnt in uni, your skillset, how you're learning outside of uni, what you're proficient in etc.
They want to see that you're actually interested and passionate in this field. They're not going to give an internship to someone who has done nothing to further their knowledge and skillset outside of uni.
You'll have to do some kind of technical challenge as part of the application process or in the interview process. In most cases, from what i've personally experienced, this will be a CTF of some kind.
Or I know when I applied to CrowdStrike, they had a website with 7 or so different categories with different subjects and you had to do tasks in a certain amount of time. They looked at your accuracy, completion rate and points gained. The categories were Linux, Powershell, Registry Persistence, Log Analysis, Splunk Analysis, Malware Analysis & Methodology.