If you're using it for 'amplification', please bear in mind this is a 'Sound Reinforcement' application, as the microphone can also 'hear' the loudspeakers.

You'll have to go for a compromise on sound level - it won't be as loud as individually miking the instruments and using an audio mixer for balance, but will give the overall sound a 'lift'.

Ideally you need an amplifier (mixer-amplifier or separates) with a graphic EQ, or a 'sweep mid' EQ on the mic channel you are using, also known as a 'parametric' or 'paragraphic' EQ. This will enable you to filter out the prominent feedback frequency (frequencies).

You should not try to EQ things too much, as it will sound unnatural - but careful EQ settings will give you more sound level.

MAKE SURE that the microphone is as far away from the front of the speakers as is possible - behind them if you can.

It's preferable to use more speakers at lower sound level ('Low Level Distribution') than trying to do it all, say, with a combo amplifier (one like guitarists use with the amp and speaker in the same cabinet).

PM me if you need guidance on specifics - it's me day job!