how do i write

[Unregistered]

how do i write , that i am at office from 8 or since 8 am , what do u suggest

[Casiopea]

What about?

I have been at/in the office since 8 a.m. (this morning).
I am at/in the office at 8 a.m. (every morning).
I am at/in the office by 8 a.m. (every morning).
I get to the office at 8 a.m. (every morning).
I will be in/at the office at 8 a.m. (today).

All the best.