if u can select a brush; then do it, then at the top icons bar with the lots of thingies, click on the select faces icon (*). then shift+left click on the face in the 3d window which u wanna select. then left click on the texture which u wanna apply. if u can not; then somebody else will be who helps u, sorry.
*: the select faces, points (called vertexes), and edges are 3 select thingie whose icons/pictograms are side by side each other in one group. iirc its a red cube. if you can guess/find these (nowhere near impossible), you have luck. if you can not, then probably you will click on one of the csg group which is another threesome gruppe, which is not good, it wont make u happy xD.
when u wanna return to normal, just hit esc button many times. anyway, spamming it is a good practice.
edit - late.