My advice would be to start lifting weights.
Mon: chest, triceps, abs
Wed: biceps, back, abs
Fri: shoulders, legs, abs
(simple as this)
You don't need to start going the gym and you deffo don't need to spend alot of money. Get your self a simple set of barbells. Two small barbells shouldn't cost too much, get yourself a big long one too, although I don't use 'em as much as the two smaller ones, I think an EZBar (werid zigzag ones) are good too. Make sure they allow you too change the amount of weight on them by swapping plates and you have enough plates to make them real light or heavy depending on what you are doing. Even new they aren't too expensive but I am sure you could get 'em used at a carboot sale or collect on
eBay.
Eat more, not junk food but for carbs stuff like oats, potatos, noodles, brown bread, rice, pasta. For protein you deffo need meat in there porks and beefs are good, beans, milk too, you could also get protein powder and I DEFFO would if your a veg. and don't eat meat. Plenty of veg. too, you'll need to eat a little more than normal (remember - good foods). You should slowly put on weight you'll gain fat too from foods but muscle since you work out however your in a cycling fourm so my guess is that'll take care of itself.
Plenty of videos of exercises for example let's say biceps can be found on Youtube, Google: Scoobys Workshop <<< good site.
Simple tips: keep good form, even if it's harder and you can't do as many reps - time under tension = win.
30-60 mins should be enough time for working out, you want it so your muscles you worked are felt the following day.
START light. Don't start out lifting heavy. FORM is important - if it's easy, next time stock more weight on, don't go in the deep end here or your bicep exercises will work your legs.
Eat some carbs and drink coffee before working out for that extra pump then protein after.
Measure your progess. Don't weigh yourself often just weekly/monthly. Between building your abdominal muscles and losing more fat you'll have a 6pack (if you don't already). Take pics, maybe every xx weeks?