Your package will display a yellow sign and say ‘Mined Block!’ and you will also be able to see it on the package's mining graph as a yellow bar with a rocket symbol on the top.
In order to mine a block, your package 'difficulty' must be at least above 100%, although having 100% alone does not mean you will mine a block, you must also have the rocket symbol. Read more about what the graph means and what your package is doing here.
There may be cases where you will see 100% but did not mine any blocks. This can be for many reasons, such as 'orphan blocks' or invalid blocks, which do happen from time to time on various blockchains. The easiest way to remember is: No Rocket = No Reward.

Rocket icon:

Once your package has completed, you will still need to wait for the block reward to be confirmed on the blockchain. Before buying any EasyMining packages your account must be verified and KYC must be completed.