Question about SRTM Resolution

Dear Mr/Ms.

My name is Kania.

Now I am studying about water resources management.

I am doing my project now.

My project need to use GIS, but unfortunately I am not really good of it.

I would like to ask you about the resolution of SRTM.

I have to use this SRTM to another model.

I already make a clip of the study area, but when I run the model, it said "the cells too big".

The solution is I have to change the resolution of the SRTM.

I use SRTM 90m.

Actually I read a discussion like this before in this website, but I am not understand all.

I would appreciate if you can give me the explanation step-by-step of it.

I plan to change the resolution into the lowest resolution (1 km or 250 m).

I am using GIS 9.3

Thank you.

Best Regards,
Kania