I am planting my beans and peas today. First timer. All help appreciated!

[WellTidy]

I have seeds, compost and deep root plug trays and a saucer. I have raised beds for when they’re ready to be planted out.

I think I can do the planting, but I am clueless as to how to look after them after they’re planted.

Do I water daily, or more frequently? And do I just put water in the saucer or the top of the plant itself too? And when it says to keep them in a window sill, what aspect should the window sill have or will any window sill do?

Just don't let them dry out. Plugs do dry out quickly due to small amount of compost space, but once a day should be enough in hot weather. If they're still moist when you check then don't add more water, you don't want the roots to rot. You can water from the top. A window sill that gets some light is preferable to one in constant shade.