Any links and recommendations preparing for a metric century ride?

be easy on me as I am quite the novice at trying this kind of thing (although not a complete cycling beginner)

I have done about 50km several times with maybe a little break in the middle, but i would like to push it to double this amount and get to 100km.

What would you recommend as a first time attempt at that? what would your training look like if you cannot just go out every day and ride longer and longer? (which is what my simple mind thought would be the best way to train to eventually reach that distance)

Any and all tips welcome. I have no timeframe for this, whenever I am ready will be the time (given northern hemisphere weather, will probably wait at least until spring)