About the creaking:
It's likely to be the crank bolts but first check that the pedals are tightened to spec.
Tighten the crankbolt to spec. The correct way to do this job depends on which particular bottom bracket setup you have fitted. With square taper cranks, for instance, the longlasting way is to take the cranks off, grease the spindles, refit the cranks, and torque them to the bottom end of the spec, try them, and tighten progressively further until they are silent.
Since you didn't know this bit of basic bicycle lore, and have health problems, I venture a couple more tips.
Generally, for bike use, everywhere but around the bottom bracket and pedals, these day a 2-16Nm torque wrench will do; that's a very small one. A useful one is by BBB; I have a much older version of the same set, still in good nick after a couple of decades of use.
SJS sells something very similar at
http://www.sjscycles.co.uk/m:part-torque-wrench-prod37956/ (I suspect that all these cycle kit small torque wrenches come from the same place; brand name and packaging determines price...) With all these small torque kits you have to add a couple of bits, usually 2 and 2.5mm hex and T20 for the Rolloff; my extra bits are the best, from Witte in Germany, because a stripped-out Rohloff part costs plenty!
Around the bottom bracket and pedals, the norm is the next torque wrench up, to at least up to 40Nm; for this I use an automotive Draper type from a common hardware store. I have several of these left over from my previous life as a hotrodder. The click stop ones with built in ratchets are superior for people with medical problems to the swing pointer types, but the latter are often cheaper and measure just as well (and sometimes better because they are such simple mechanism, difficult to go wrong).
If you buy only one torque wrench, stick to the smaller one. Torque settings are much more critical around the low end.
Be sure that you have read all the spec sheets and bumf and made a list of required torque setting (I keep mine in the actual torque wrench case) before you start shopping for a torque wrench.
Unless you're really rich, you don't need the fancy-smancie Gusta Forza.
***
The thing about health problems is that generally they may stop you from lifting the bike up on the stand, especially if it is set very high so you can work on the cranks without bending, and also they interfere with bending over the bike when it is standing on the ground. Furthermore, in that position you can't strain to get 30-35Nm on the crank bolts; pedals, if you want to torque them precisely via a hex in the end of the threaded end of the axle, can be very awkward too.
I solved the crank bolt/pedal bolt problem quite simply. Fold up you wife's rotary dryer and check that the pole is concreted-in firmly because it needs to stabilize you and the bike, with both your feet of the ground. If you can't find a suitable pole in your backyard, go out on the street, where you will find all kinds of solidly-concreted-in polses for signs and for lamps.
Put a piece of tubular slit foam such as your bike arrived in around the top tube. Lean the bike against the pole. Arrange the cranks so that the pole blocks one pedal at the top of its turn (turn the bike around if you need to) with the crank or pedal you want to mechanic on at the bottom -- yes, that's right, at the bottom. Set up the tool in the hex or on the nut; it will generally just hang there; if it falls out you need a helper. Stand on the lower pedal with one foot while holding on to the pole with both hands. Now put your other foot on the tool and press progressively. Your legs are much stronger than your arms, even your back when you're bent over. When you hear the torque wrench click, the job is done. If you're using a swing pointer torque wrench, you need a helper to watch it. All of this is much quicker and easier to do than to describe. I once stood on the pavement in front of my bank and used the "No bicycles" sign's pole to brace the pedal while I adjusted the crank bolt tension. A police car stopped and a young policeman came over to me. "Can you show me that again, so I can show my dad? He's got a bad back."
