It is not at all difficult or complex. But you do need a hammer drill, fitted with a masonry bit.
Consider that the screw and the plasplug must go at least an inch into the brick or block, and that the plaster might be about 20mm thick, and the curtain bracket might be 6mm. Therefore you need about a 50mm screw and hole. Sometimes 40mm will do. Use brown plugs. You will tap the plasplugs slightly below the level of the plaster, which prevents cracking and makes it easier to fill and decorate in future. If the wall is plasterboard spaced off blockwork, drill through the board first and measure the depth of gap to calculate the screw length required. If the board is on wooden studs, find the studs and screw into them (no plug required).
When plugging a wall, if the plug is a loose fit and turns when you try to screw into it, clear all the dust and grit out with your hoover hose, then fill the hole (starting at the back) with a no-more-nails type adhesive, then press your plasplugs into the adhesive, and slightly below the surface (using a screw a couple of turns into the plug as a handle). Wipe away the excess glue with a damp sponge, leave overnight to set before fitting the bracket and driving the screw home.
If you drill through the plaster above a window and hit a steel lintel, remove the masonry bit and fit an HSS twist drill. You can still use a plasplug and screw.
The size of drill and width of screw required are marked on the flat strip on the pack of plasplugs.