as far as I see from your comment, you seem to be not too familiar with such work, so I hope you won't mind if I'd comment more detailed.
First of all: the seal ring shown in your picture has been mounted in the right direction. Such seals have a pressure side (reinforced with a metallic spring coil) and an athmosperic pressure side. So inside of a crankcase we have the pressure side with the fuel-air-oil mix which should stay inside, and from the other side which is the outside, we have the athmosperic side. Got it [;)] ?
But careful : for Vespa PX there are 2 different types of seals. The example shown in the pictures is the "bare metal" version, which fits in crankcases without an extra groove in the matching seat; whilst the completely rubber coated version needs this groove in the matching seat.
In every case you should test if the bearing below the seal is free spinning, without any resistance which may be generated by the wrong type of seal or the wrong method of assembly. Also, when the crankshaft has been assembled, no part of the seal should grind/touch the crankshaft, besides it's sealing lip.
Also in every case ensure that all of the parts (seal and mounting seat) are free of grease, dust, oil, dirt, humidity etc. Clean and correct assembly is abolutely sufficient to have a reliable seal. There is absolutely no need to experimentate with adhesives.
Also you should not remove the coil spring - leave the seal ring untouched and don't mess around with this sensitive part. When you assemble the crank shaft, please don't forget to apply some engine oil (NO grease) on the seal lips of the seal as well as to the corresponding gliding faces on the crankshaft.
Also it is strongly recommendable to assemble the crankshaft by pulling it into there bearing (a special tool is needed which should always support itself against the inner sleeve of the bearing) - never do this with hammering the crankshaft in from the opposite (Remind: the crankshaft consists of single parts which have been pressed together. The wrong way of assembly will lead to a distortion of the position of the main parts of the crankshaft. If this happens, the crankshaft would stumble around in the crankcase. Then strong vibrations will occur, that damage the sensitive crankcase)