GRAPHIC software

Hello Settlers

Screenshots are raster images. For an adventure guide I need to add all kinds of markings, especially very nice fluid lines and arrows.
Which small graphic app is best to get those lines, marks, text etc.. upon raster images ?? It could be a complex operation but I hope it is possible in a more simple way.
Would be fine if I could find a free software app to get a great result. Thank you for some information.

Settler Bo.

Corel Painter, Photoshop, Paint.NET, MS Paint and GIMP to name a few

I always just use lightshot and MS Paint

Lightshot and IrfanView, both free apps