Remove the cover of Triton Topaz 100i?

I have a topaz 100i which is showing the low pressure light regularly. In this particular instance I fear it may genuinely be because of low pressure!

However, I want to do all that I can to make use of the pressure we do have - and some postings make mention of cleaning out the inlet filter. Could anyone provide some layman's instructions on how to do this? To give you a feel on how basic we're talking - I don't even know how to remove the front cover.