As well as basic information you will find links to other sites. (Click on the underlined words)
Some of these are also conservation minded, some offer help and advice and some are just good videos of swifts. All of these videos have sound.
Start here
What to do if you find a swift on the ground
A healthy bird is quite capable of taking off from level ground. Swifts are complex birds and many factors could have caused the bird to ground.
Probably it is a young bird who didn't quite make its first flight.
Gently pick up the grounded swift and place in a suitable box on some warm fabric.
A professional swift carer should then be consulted before attempting to treat or feed the swift.
Wild birds require specialized treatment and really specific diets to help them recover from injuries or trauma.
See video supplied by someone who knows what he is doing.
Don't try this at home!
Property Repairs
Nest Boxes
Some ideas. You can build your own, buy ready made ones or improvise.
RSPB ready made Nest box A Dutch Nest box
Swifts inspecting a Nest box (Video)
Videos
These are YouTube videos so apologies if you get adverts first.