Toilet water level too low

[Mrssmith75]

Hi. Toilet water level has been way too low since it was put in. Other half is working all hours so trying to resolve myself.
Watched videos today of how to do it on push button flush.
Instructions say to find button/something to slide/press to enable the collar to lift up and down.
There is nothing. Therefore I cannot do it.
The only option I can see is to replace the whole right part. Need help:
What is it called? Float?
How do I replace?

 

[Echo the husky]

A photo of the unit you have would help!