If you're block printing on fabric, you'll want to use a block printing ink that is safe to use on fabrics.
It will say it's for fabric use right on the tube, like this one for example.
Another option for block printing fabric is using an ink pad that can be used on fabrics, like this one.
Using ink pads for block printing are best for small lino blocks (2-3 inches in size).
If you're using larger blocks, you'll probably want to go the traditional route of inking, which I'll explain below.
*Also, this method of using an ink pad isn't really a true form of block printing. BUT it is a nice option when you're in a hurry, or want to save money with the purchase of a few less tools.
If you're using a fabric ink pad and small linoleum block, open up the ink pad and continuing dabbing ink onto the lino block until the design is fully (and evenly) covered.
If you're using a more traditional method for inking, squeeze out a thin line of ink (whether its fabric ink or regular printing ink for paper) toward the top of the acrylic sheet (or glass) palette.
Then use the soft rubber brayer (the roller), to bring the ink down.
Rolling the ink out a bit on the surface of your palette before rolling it over your stamp in thin layers until the raised design is fully covered.
Make sure the linoleum block isn't over inked or you could lose some of the fine details of your design when printing.
You'll notice when you roll the ink out that it has a much different viscosity than regular paint. It's much more tacky.