Basically you use coin control and select all your inputs and send them to one address.
The wallet will show you on the dashboard how much coins a staked block needs to be at
to stake at a certain percent, so if combining inputs will not put you at the next level you are better off
leaving your inputs alone.
Those numbers will get higher as coin supply increases so you will need to keep a close eye on them.
In the first 15 days of vPoS your initial PoW investment will increase at a great rate,
then there will be a sudden drop of 90% interest on all slabs.
* The wallet will not split an input when it's staked so no need to re-combine unless you want to add more coins.
so min block on wallet main screen is amount of coins in each address, right ?