A sudden restrictive diet is sometimes not the best thing as if your blood glucose reduces too quickly then some people do get some vision issues.
The best way is to start by making an honest food diary of everything you eat and drink (as in prediagnosis) and estimate how much carbohydrate you were having, info can be found on packets or the internet by searching for TOTAL carbohydrate which will usually be in g/100g so you would need to work out for the portion you have had. It is then suggested that you reduce the amount by one third for a couple of weeks, then another third for a few weeks.
Reducing your intake of high carb foods such as potatoes, rice, pasta, bread, cereals and fruits like bananas and tropical fruit as well as cakes and biscuits and snacks like crisps.
It might sound as if there is nothing that you can eat but basing your meals on meat, fish, eggs, cheese, full fat dairy and fruits like berries as well as vegetables and salads you can have tasty filling meals.
Many people find that low carbohydrate normal fat (not low fat) dietary regime is a sustainable way that will lower their blood glucose levels.
A bit of information about your diagnosis, what is your HbA1C and are you on any medication will help people tailor any suggestions.
Have a look at the Learning Zone (orange tab at the top) and work your way through the info for Type 2, then please come back with any questions you have.