You can make a simple monetary donation, to this very worthy and very important human rights organization:
https://secure.actblue.com/donate/ms_blm_homepage_2019

Or, if you prefer, you can make a purchase of merchandise — since the organization does make a smaller amount of profit from every purchase. (This includes such things as T-Shirts, and hats — all of which are actually kind of “spiffy” in design.)
https://blacklivesmatter.shop.capthat.com/store/

Or, if you prefer — you can simply volunteer. Here is the contact procedure.
https://blacklivesmatter.com/contact/

Remember — their mission is always to remain non-violent. No matter what. So, if you volunteer for any of the organized protests, be certain to make that 100% clear that you understand that. Right now, that is a huge issue, since so many others with a violent agenda have been infiltrating and invading and trying to hijack their organized, peaceful protests.
You must agree to remain non-violent, and also must agree to make that clear to all others who are there with you.