When you say altcoins, there are many types of altcoins. POS coin, erc20 token etc. You have to be specific in order for us to find out what wallet you need. So you bought LTC,  coinomi has LTC wallet i suggest you put your LTC there. If you bought an erc20 token use myetherwallet or imtoken. If you bought a pos coin (proof of stake) i suggest you download windows wallet it is the safest wallet .