If you look on an online map of the lake (actually, it used to be sea and it is only that it is behind a dike that it is now called a lake) and you will see that there are many smaller and some bigger towns and cities on the coast. All cities, most towns and villages and municipalities will have a website, mostly also available in English, where you will find the principle touristy information as well as local practical information. Most marinas and other harbours will also have websites and searching on a name on a map will mostly give you the websites.
Zoom in on any of the towns and you will see a marina or a few, more in bigger towns and cities. Most of those will be paid but some 'free places for limited time' are available. Once you have had a look and see how much is available, you will want a good site or book which does include details like prices, opening times and facilities.
A look at a map or chard for the area will show you plenty of marinas, if you do your planning right you can do almost no distance or quite big distances, but remember that not all marinas will have spaces at the end of the day. Many have plenty of regulars for which they hold berths, some of which might be available for one night while others will have the regulars come back to at night.
If nobody in your group is fluent in Dutch, make sure you have a way to translate signs and texts in harbours and marinas.
When sailing you need good chards, and an almanac with all the bridge and lock times for the area you are. I know there is a book, published every year, but I do not know whether you need that full book or can find things online.
While this is called 'meer' (lake in English) it is still very open to the North Sea and it is well known for very strong winds (storms) blowing up and causing havoc, and while you can be in sight of land for most of the time, you need proper navigation aids. (Some people only have a phone and find the connection fails when out on the water, especially when the weather turns bad.)
You will need to check the weather reports, more so than for lakes which are behind mountains from the sea, as weather comes in very fast and reports of boats that had come to a bad end are quite common (one or more every bad summer storm.)
I do not sail but friends and relatives do and they all have respect for this water, as it is more challenging than many people allow for.
Almost every thing you may want to know and all you need to know will be on internet by now, most of it also in English. And online translation software will translate almost everything, so your first steps may well be to look for information is available for you.
As with all rentals, you go to the site of a place where they rent out what you need. You will find many rental sites on and near the coasts, they will each state what kind of boats they offer and what restrictions they have (some may ask for a certain level of experience.) If you have experience on a certain kind of boat, or your fellow skipper, maybe look at a boat which is pretty much like it, so you know what to expect from it.