Basically you put your freebase into a little water, then add HCl one drop at a time, stirring with each drop. As the salt forms, the DMT dissolves. Aim for pH 6 or 7. There's a little more detailed info on this procedure if you do a search on IVing DMT (there's a link or two in the DMT and DMSO thread).
DMT HCl cannot be isolated as a solid. The only DMT salt which has been reported as a solid is DMT fumarate.